#include <iostream>
#include <fstream>
#include <vector>
#include <queue>
#include <algorithm>
#include <bits/stdc++.h>
#include <tuple>

std::ifstream f("darb.in");
std::ofstream g("darb.out");

using namespace std;
class graf{
private:
    int n,m,distmax,nod;
    vector <int> vizitate;
    vector <int> distanta;
    vector <vector <int> > muchii;
public:
    graf(int n);
    void citire_muchii(int n);
    void DFS_distanta(int s, int dist);
    int gasire_dist_max();
    int gasire_nod();

};
graf::graf(int n)
{
    this->n=n;
}
void graf::citire_muchii(int n)
{
    int start_edge, end_edge;
    f>>n;
    for(int i=1;i<n;i++)
        {f>>start_edge>>end_edge;
        muchii[start_edge].push_back(end_edge);}
}
void graf::DFS_distanta(int s, int dist)
{   distanta[s]=dist;
    vizitate[s] = 1;
    for (int i : muchii[s])
    {
        if (vizitate[i] == 0)
        {
            DFS_distanta(i, dist+1);
        }
    }
}
int graf:: gasire_dist_max(){
    for(int i=0;i<=n;i++)
    {
        if (distanta[i]>distmax)
        {
            distmax=distanta[i];
            nod=i;
        }
    }
    return distmax;}

int graf:: gasire_nod(){
    for(int i=0;i<=n;i++)
    {
        if (distanta[i]>distmax)
        {
            nod=i;
        }
    }
    return nod;}
int main()
{

    int n,m,distmax=0,nodcudistmax=0;
    graf gr(n);
    vector <int> vizitate;
    vector <int> distanta;
    distanta.resize(n+1);
    vizitate.resize(n+1);
    gr.DFS_distanta(1,0);
    int nod=gr.gasire_nod();
    for(int i=0;i<=n;i++) //ca sa putem aplica dfs din nou fara probleme din nodul final
    {
        distanta[i]=0;
        vizitate[i] = 0;
    }
    gr.DFS_distanta(nod, 0);
    int maxim=gr.gasire_dist_max();
    g << "diametrul este:" << maxim; //????????/ eroare
    f.close();
    g.close();
    return 0;
}