#include <fstream>
#include <iostream>
#include <algorithm>
#include <climits>
#include <vector>
#include <list>
#include <stack>
#include <queue>
#include <set>
using namespace std;

constexpr auto INF = INT_MAX;
constexpr bool Directed = true, unDirected = false, Weighted = true, unWeighted = false, Flowing = true, unFlowing = false;


ifstream fin("darb.in");
ofstream fout("darb.out");



class Edge
{
    // easier, cleaner and more expandable alternative to using a tuple for Storing sourceNodes, destinationNodes, weights, capacities etc...

public:

    int src;
    int dest;
    int cost;
    int cap;

    Edge () : src(0), dest(0), cost(0), cap(0) {}
    Edge (int s, int d, int c = 0, int g = 0) : src(s), dest(d), cost(c), cap(g) {}
};

bool costASC(Edge x, Edge y)
{
    return x.cost < y.cost;
}



class Graph
{
    // Implementation of  << UTILITARY Functions >>  for (UN)Directed, (UN)Weighted & (UN)Flowing  << Graphs >> ;

    bool isDirected;
    bool isWeighted;
    bool isFlowing;

    int nrNodes;
    int nrEdges;

    vector<list<Edge>> adjacencyList;


public:

    Graph(int n = 0, int m = 0, bool d = false, bool w = false, bool f = false) : nrNodes(n), nrEdges(m), isDirected(d), isWeighted(w), isFlowing(f) {}

    void readAdjacencyList();

    void printAdjacencyList();


    vector<int> getUnweightedDistances(int startingNode);

    list<set<int>> getConnectedComponents();

    list<set<int>> getStronglyConnectedComponents();

    list<set<int>> getBiconnectedComponents();

    list<pair<int, int>> getCriticalEdges();

    list<int> getTopologicalOrder();

    bool getValidGraph();

    void getDisjointSets(int nrOp); // de lucrat cu afisarea si citirea (also denumirea <get>)

    vector<int> getWeightedDistances(int startingNode);

    vector<int> getBellmanFordDistances(int startingNode);

    vector<pair<int, int>> getMinimumSpanningTree(int& minimumCost);

    int getTreeDiameter();


private:

    void BFS(int startingNode, vector<int>& dist);

    void DFS(int currentNode, vector<bool>& isVisited, set<int>& connectedComponent);

    void TarjanDFS(int currentNode, vector<int>& discOrder, vector<int>& lowLink, stack<int>& path, vector<bool>& onStack, list<set<int>>& SCClist);

    void BiconnectedDFS(int currentNode, int currentLevel, vector<int>& level, vector<int>& lowLink, stack<int>& path, list<set<int>>& BCClist);

    void CriticalEdgesDFS(int startingNode, int previous, vector<int>& discOrder, vector<int>& lowLink, list<pair<int, int>>& CElist);

    void TopologicalOrderDFS(int startingNode, vector<bool>& isVisited, list<int>& TOlist);

    void HavelHakimi(vector<int>& degrees, bool& valid);

    int Find(int targetNode, vector<int>& parent);

    void Union(int targetNode1, int targetNode2, vector<int>& parent);

    void Dijkstra(int startingNode, vector<int>& dist);

    void BellmanFord(int startingNode, vector<int>& dist);

    void Kruskal(int& minimumCost, vector<Edge>& edgeList, vector<int>& parent, vector<pair<int, int>>& MSTlist);

};


#pragma region Utilitary_Functions

void Graph :: readAdjacencyList()
{
    adjacencyList.resize(nrNodes + 1);


    for (int i = 0; i < nrEdges; i++)
    {
        Edge edge;
        fin >> edge.src >> edge.dest;

        if (isWeighted)
            fin >> edge.cost;

        adjacencyList[edge.src].push_back(edge);

        if (!isDirected)
        {
            Edge rev = edge;
            swap(rev.src, rev.dest);

            adjacencyList[edge.dest].push_back(rev);
        }
    }
}

void Graph :: printAdjacencyList()
{
    fout << "\n>   nrNodes = " << nrNodes;
    fout << "\n>   nrEdges = " << nrEdges;

    fout << "\n\n\n>   The ADJACENCY LIST associated to the ";
    isDirected ? fout << "DIRECTED" : fout << "UNDIRECTED";
    isWeighted ? fout << ", WEIGHTED" : fout << ", UNWEIGHTED";
    fout << " graph <G>:";

    for (int i = 1; i <= nrNodes; i++)
        if (adjacencyList[i].size())
        {
            fout << "\n\nNode " << i << ":\n";
            for (auto& edge : adjacencyList[i])
            {
                fout << edge.src << " ---> " << edge.dest;
                if (isWeighted && isFlowing)
                    fout << "  (" << edge.cost << ", " << edge.cap << ")";
                else if (isWeighted)
                    fout << "  |" << edge.cost << "|";
                else if (isFlowing)
                    fout << "  /" << edge.cap << "/";
                fout << "\n";
            }
        }
}


vector<int> Graph :: getUnweightedDistances(int startingNode)
{
    vector<int> distances(nrNodes + 1, -1);

    Graph :: BFS(startingNode, distances);

    return distances;
}

list<set<int>> Graph :: getConnectedComponents()
{
    list<set<int>> CClist;
    vector<bool> isVisited(nrNodes + 1, false);

    for (int i = 1; i <= nrNodes; i++)
        if (!isVisited[i])
        {
            set<int> connectedComponent;
            Graph :: DFS(i, isVisited, connectedComponent);

            CClist.push_back(connectedComponent);
        }

    return CClist;
}

list<set<int>> Graph :: getStronglyConnectedComponents()
{
    list<set<int>> SCClist;

    vector<int> discoveryOrder(nrNodes + 1, 0);
    vector<int> lowestLink(nrNodes + 1, 0);
    vector<bool> onStack(nrNodes + 1, false);
    stack<int> path;

    for (int i = 1; i <= nrNodes; i++)
        if (!discoveryOrder[i])
            Graph :: TarjanDFS(i, discoveryOrder, lowestLink, path, onStack, SCClist);

    return SCClist;
}

list<set<int>> Graph :: getBiconnectedComponents()
{
    list<set<int>> BCClist;

    vector<int> levels(nrNodes + 1, 0);
    vector<int> lowestLink(nrNodes + 1, 0);
    stack<int> path;

    Graph :: BiconnectedDFS(1, 1, levels, lowestLink, path, BCClist);

    return BCClist;
}

list<pair<int, int>> Graph :: getCriticalEdges()
{
    list<pair<int, int>> CElist;

    vector<int> discoveryOrder(nrNodes + 1, 0);
    vector<int> lowestLink(nrNodes + 1, 0);

    Graph :: CriticalEdgesDFS(1, 0, discoveryOrder, lowestLink, CElist);

    return CElist;
}

list<int> Graph :: getTopologicalOrder()
{
    list<int> TOlist;
    vector<bool> isVisited(nrNodes + 1, false);

    for (int i = 1; i <= nrNodes; i++)
        if (!isVisited[i])
            Graph :: TopologicalOrderDFS(i, isVisited, TOlist);

    return TOlist;
}

bool Graph :: getValidGraph()
{
    bool validity;
    vector<int> degrees;

    int deg;
    while (fin >> deg)
        degrees.push_back(deg);

    Graph :: HavelHakimi(degrees, validity);

    return validity;
}

void Graph :: getDisjointSets(int nrOp)
{
    vector<int> parent;
    parent.push_back(0);

    for (int i = 1; i <= nrNodes; i++)
        parent.push_back(i);


    for (int i = 0; i < nrOp; i++)
    {
        int op, x, y;
        fin >> op >> x >> y;

        if (op == 1)
            Graph :: Union(x, y, parent);
        else
        {
            if (Graph :: Find(x, parent) == Graph :: Find(y, parent))
                fout << "DA\n";
            else
                fout << "NU\n";
        }
    }
}

vector<int> Graph :: getWeightedDistances(int startingNode)
{
    vector<int> distance(nrNodes + 1, INF);
    Graph :: Dijkstra(startingNode, distance);

    return distance;
}
                                                                            // merge them together by cost (negative)
vector<int> Graph :: getBellmanFordDistances(int startingNode)
{
    vector<int> distance(nrNodes + 1, INF);

    Graph :: BellmanFord(startingNode, distance);

    return distance;
}

vector<pair<int, int>> Graph :: getMinimumSpanningTree(int& minimumCost)
{
    vector<int> parent(nrNodes + 1, 0);
    vector<pair<int, int>> MSTlist;
    vector<Edge> edgeList;

    for (int i = 1; i <= nrNodes; ++i)
        parent[i] = i;

    for (int i = 1; i <= nrNodes; i++)
        for (auto& edge : adjacencyList[i])
            edgeList.push_back(edge);

    Graph :: Kruskal(minimumCost, edgeList, parent, MSTlist);

    return MSTlist;
}

int Graph :: getTreeDiameter()
{
    vector<int> bfs1, bfs2;
    pair<int, int> maxInd = { 0, 0 };

    bfs1 = getUnweightedDistances(1);
    //auto maxInd = distance(bfs1.begin(), max_element(bfs1.begin(), bfs1.end())) + 1;    // index of element with max-value
    for (int i = 0; i < nrNodes; i++)
        if (bfs1[i] > maxInd.first)
        {
            maxInd.first = bfs1[i];
            maxInd.second = i;
        }

    bfs2 = getUnweightedDistances(maxInd.second + 1);
    //diameter = *max_element(bfs2.begin(), bfs2.end()) + 1;
    for (int i = 0; i < nrNodes; i++)
        if (bfs2[i] > maxInd.first)
            maxInd.first = bfs2[i];

    return maxInd.first + 1;
}


void Graph :: BFS(int startingNode, vector<int>& dist)
{
    queue<int> inProcessing;    // stores the order of the bfs traversal

    inProcessing.push(startingNode);
    dist[startingNode] = 0;

    while (!inProcessing.empty())
    {
        int last = inProcessing.front();    // extracts the first node from the queue, to push its adjacent nodes in the queue
        inProcessing.pop();

        for (auto& edge : adjacencyList[last])
            if (dist[edge.dest] == -1)    // checks for unvisited adjacent nodes
            {
                inProcessing.push(edge.dest);
                dist[edge.dest] = dist[last] + 1;
            }
    }

    dist.erase(dist.begin());
}

void Graph :: DFS(int currentNode, vector<bool>& isVisited, set<int>& connectedComponent)
{
    isVisited[currentNode] = true;    // every time recursion takes place on an unvisited node, it's marked as visited, not to be includee in more than 1 connected component;
    connectedComponent.insert(currentNode);

    for (auto& edge : adjacencyList[currentNode])    // traverses every node in the current node's adjacency list and (if it hadn't already been included in a connected component), continues recursion from it;
        if (!isVisited[edge.dest])
            DFS(edge.dest, isVisited, connectedComponent);
}

void Graph :: TarjanDFS(int currentNode, vector<int>& discOrder, vector<int>& lowLink, stack<int>& path, vector<bool>& onStack, list<set<int>>& SCClist)
{
    static int currentID = 1;    // increments and keeps value after each recursion
    discOrder[currentNode] = lowLink[currentNode] = currentID++;    // discOrder: assigns an ID to each node, representing the DFS traversal order;   lowLink: point to the lowest ID that a node can return to

    path.push(currentNode);    // stores the DFS traversal path
    onStack[currentNode] = true;    // to check if a node is on the current traversal path


    for (auto& edge : adjacencyList[currentNode])    // for each node adjacent to the current node
    {
        if (discOrder[edge.dest])    // if the adjacent node had been processed and is part of the current traversal path
            if (onStack[edge.dest])
                lowLink[edge.src] = min(lowLink[edge.src], discOrder[edge.dest]);    // update the lowest returning point of the adjacent node

            else    // if the adjacent node hadn't been processed yet, start recursion from it
            {
                TarjanDFS(edge.dest, discOrder, lowLink, path, onStack, SCClist);
                lowLink[edge.src] = min(lowLink[edge.src], lowLink[edge.dest]);    // after the recursion callback, update the lowest returning point of the adjacent node
            }
    }


    if (lowLink[currentNode] == discOrder[currentNode])    // if the lowest returning point of a node is also its discovery ID, it means that the node is the root of its strongly connected component
    {
        set<int> connectedComp;
        int last;

        do    // removes all the nodes, until the SCC's root, from the path's stack and inserts them into a new strongly connected component
        {
            last = path.top();
            path.pop();
            onStack[last] = false;

            connectedComp.insert(last);
        } while (currentNode != last);

        SCClist.push_back(connectedComp);
    }
}

void Graph :: BiconnectedDFS(int currentNode, int currentLevel, vector<int>& level, vector<int>& lowLink, stack<int>& path, list<set<int>>& BCClist)
{
    path.push(currentNode);    // stores the DFS traversal path
    level[currentNode] = lowLink[currentNode] = currentLevel;    // level: the "depth" of each node in the DFS traversal's tree;   lowLink: point to the lowest "depth" that a node can return to

    for (auto& edge : adjacencyList[currentNode])
    {
        if (level[edge.dest]) // daca nodul vecin a fost explorat
            lowLink[edge.src] = min(lowLink[edge.src], level[edge.dest]); // adancimea minima a nodului curent S = min (adancimea sa minima curenta; adancimea vecinilor sai)

        else
        {
            BiconnectedDFS(edge.dest, currentLevel + 1, level, lowLink, path, BCClist);
            lowLink[edge.src] = min(lowLink[edge.src], lowLink[edge.dest]); // la intoarcerea din recursie, nodurile cu adancimea < adancimea nodului pe care s-a facut recursia
                                                                            // isi minimizeaza adancimea minima lowLink cu a succesorilor;
            if (lowLink[edge.dest] == level[edge.src]) // cand ajungem la succesorul radacinii componentei, eliminam nodurile pana la radacina din stiva, formand o componenta biconexa;
            {
                set<int> biconnectedComp;
                int last;

                do
                {
                    last = path.top();
                    path.pop();

                    biconnectedComp.insert(last);
                } while (edge.dest != last);

                biconnectedComp.insert(edge.src);
                BCClist.push_back(biconnectedComp);
            }
        }
    }
}

void Graph :: CriticalEdgesDFS(int startingNode, int previous, vector<int>& discOrder, vector<int>& lowLink, list<pair<int, int>>& CElist)
{
    static int currentID = 1;
    discOrder[startingNode] = lowLink[startingNode] = currentID++;

    for (auto& edge : adjacencyList[startingNode])
    {
        if (discOrder[edge.dest])
        {
            if (edge.dest != previous)
                lowLink[edge.src] = min(lowLink[edge.src], discOrder[edge.dest]);
        }
        else
        {
            CriticalEdgesDFS(edge.dest, edge.src, discOrder, lowLink, CElist);
            lowLink[edge.src] = min(lowLink[edge.src], lowLink[edge.dest]);

            if (lowLink[edge.dest] > discOrder[edge.src])
                CElist.push_back(make_pair(edge.src, edge.dest));
        }
    }
}

void Graph :: TopologicalOrderDFS(int startingNode, vector<bool>& isVisited, list<int>& TOlist)
{
    isVisited[startingNode] = true;

    for (auto& edge : adjacencyList[startingNode])
        if (!isVisited[edge.dest])
            TopologicalOrderDFS(edge.dest, isVisited, TOlist);

    TOlist.push_front(startingNode);
}

void Graph :: HavelHakimi(vector<int>& degrees, bool& valid)
{
    while (!degrees.empty())
    {
        sort(degrees.begin(), degrees.end(), greater<>());

        if (degrees[0] == 0)
        {
            valid = true;
            break;
        }

        if (degrees[0] > degrees.size() - 1)
        {
            valid = false;
            break;
        }

        for (int i = 1; i <= degrees[0]; i++)
        {
            degrees[i]--;

            if (degrees[i] < 0)
            {
                valid = false;
                break;
            }
        }

        degrees.erase(degrees.begin());
    }
}

int Graph :: Find(int targetNode, vector<int>& parent)
{
    if (targetNode != parent[targetNode])
        parent[targetNode] = Find(parent[targetNode], parent);

    return parent[targetNode];
}

void Graph :: Union(int targetNode1, int targetNode2, vector<int>& parent)
{
    targetNode1 = Graph :: Find(targetNode1, parent);
    targetNode2 = Graph :: Find(targetNode2, parent);


    if (targetNode1 == targetNode2)
        return;

    parent[targetNode1] = targetNode2;
}

void Graph :: Dijkstra(int startingNode, vector<int>& dist)
{
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> inProcessing;

    inProcessing.push(make_pair(0, startingNode));
    dist[startingNode] = 0;

    while (!inProcessing.empty())
    {
        int nearestNode = inProcessing.top().second;
        int currentDistance = inProcessing.top().first;
        inProcessing.pop();

        if (currentDistance <= dist[nearestNode])
        {
            for (auto& edge : adjacencyList[nearestNode])
            {

                if (dist[edge.dest] == INF && dist[nearestNode] + edge.cost < dist[edge.dest])
                {
                    dist[edge.dest] = dist[nearestNode] + edge.cost;
                    inProcessing.push(make_pair(dist[edge.dest], edge.dest));
                }
            }
        }
    }

    for (auto& d : dist)
        d == INF ? d : 0;
}

void Graph :: BellmanFord(int startingNode, vector<int>& dist)
{
    queue<int> processingQueue;
    vector<bool> inQueue(nrNodes + 1, false);
    vector<int> countIterations(nrNodes + 1, 0);

    dist[startingNode] = 0;
    processingQueue.push(startingNode);
    inQueue[startingNode] = true;


    while (!processingQueue.empty())
    {
        int currentNode = processingQueue.front();
        processingQueue.pop();
        inQueue[currentNode] = false;

        countIterations[currentNode]++;
        if (countIterations[currentNode] == nrNodes)
        {
            dist[0] = 0;
            break;
        }

        for (auto& edge : adjacencyList[currentNode])
        {
            if (dist[edge.dest] > dist[currentNode] + edge.cost)
            {
                dist[edge.dest] = dist[currentNode] + edge.cost;

                if (!inQueue[edge.dest])
                {
                    processingQueue.push(edge.dest);
                    inQueue[edge.dest] = true;
                }
            }
        }
    }
}

void Graph :: Kruskal(int& minimumCost, vector<Edge>& edgeList, vector<int>& parent, vector<pair<int, int>>& MSTlist)
{
    sort(edgeList.begin(), edgeList.end(), costASC);

    for (auto edge : edgeList)
    {
        int t1 = Graph :: Find(edge.src, parent);
        int t2 = Graph :: Find(edge.dest, parent);

        if (t1 != t2)
        {
            MSTlist.push_back(make_pair(edge.src, edge.dest));
            Graph :: Union(t1, t2, parent);
            minimumCost += edge.cost;
        }
    }
}

#pragma endregion



int main()
{
    int nodes, edges, start, operations;
    fin >> nodes;

    Graph G(nodes, nodes);     // G(nodes, edges, isDirected, isWeighted, isFlowing);

    G.readAdjacencyList();
    //G.printAdjacencyList();
    

#pragma region Public_Methods_Calls

/* ---> MINIMAL DISTANCES (UNWEIGHTED) <--- */

    /*
    vector<int> minDistances_UW = G.getUnweightedDistances(start);

    for (auto dist : minDistances_UW)
        fout << dist << " ";
    */


/* ---> CONNECTED COMPONENTS <--- */

    /*
    list<set<int>> CClist = G.getConnectedComponents();

    fout << CClist.size();
    */


/* ---> STRONGLY CONNECTED COMPONENTS <--- */

    /*
    list<set<int>> SCClist = G.getStronglyConnectedComponents();

    fout << SCClist.size() << "\n";

    for (auto SCC : SCClist)
    {
        for (auto node : SCC)
            fout << node << " ";
        fout << "\n";
    }
    */


/* ---> BICONNECTED COMPONENTS <--- */

    /*
    list<set<int>> BCClist = G.getBiconnectedComponents();

    fout << BCClist.size() << "\n";

    for (auto BCC : BCClist)
    {
        for (auto node : BCC)
            fout << node << " ";
        fout << "\n";
    }
    */


/* ---> CRITICAL EDGES <--- */

    /*
    list<pair<int, int>> CElist = G.getCriticalEdges();

    fout << CElist.size() << "\n";

    for (auto edge : CElist)
        fout << "(" << edge.first << " " << edge.second << ")" << "\n";
    */


/* ---> TOPOLOGICAL ORDER <--- */

    /*
    list<int> TOlist = G.getTopologicalOrder();

    for (auto node : TOlist)
        fout << node << " ";
    */


/* ---> GRAPHICAL SEQUENCE <-- - */

    /*
    bool HH = G.getValidGraph();

    HH ? fout << "Yes" : fout << "No";
    */


/* ---> MINIMAL DISTANCES (WEIGHTED) <--- */

    /*
    vector<int> minDistances_W = G.getWeightedDistances(1);

    for (int i = 2; i <= nodes; i++)
        fout << minDistances_W[i] << " ";
    */


/* ---> MINMAL DISTANCES (W/ NEGATIVE COSTS) <--- */

    /*
    vector<int> minDistances_NegC = G.getBellmanFordDistances(1);

    if (minDistances_NegC[0] == 0)
        fout << "Ciclu negativ!";
    else
        for (int i = 2; i <= nodes; i++)
            fout << minDistances_NegC[i] << " ";
    */


/* ---> DISJOINT SETS <--- */

    /*
    G.getDisjointSets(operations);
    */


/* ---> MINIMUM SPANNING TREE <--- */

    /*
    int minCost = 0;
    vector<pair<int, int>> MST = G.getMinimumSpanningTree(minCost);

    fout << minCost << "\n" << MST.size() << "\n";

    for (auto edge : MST)
        fout << edge.first << " " << edge.second << "\n";
    */


/* ---> TREE DIAMETER <--- */

    
    int diameter =  G.getTreeDiameter();
    fout << diameter;
    

#pragma endregion
}