#include <iostream>
#include <fstream>
#include <vector>
#include <string.h>
#define dMAX 100000

using namespace std;

int n, x, y, l, maxi, r;
vector<int> graf[dMAX + 2];

int dist[dMAX + 2];
bool viz[dMAX + 2];

char nr[30];
int o, idx;

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

void GetInt(int &p) {
    o = 0;
    while (isdigit(nr[idx])) {
        o *= 10;
        o += (int)nr[idx] - '0';
        idx++;
    }
    idx++;
    p = o;
}

void DFS(int v, int &t) {
    viz[v] = true;
    int newV, u;
    for (u = 0; u < graf[v].size(); u++) {
        newV = graf[v][u];
        if (!viz[newV]) {
            dist[newV] = dist[v] + 1;
            if (dist[newV] > maxi) {
                maxi = dist[newV];
                t = newV;
            }
            DFS(newV, t);
        }
    }
}

int main()
{
    int i, j;
    fin >> n;
    fin.get();
    for (i = 1; i <= n; i++) {
        fin.getline(nr, 30);
        idx = 0;
        GetInt(x);
        GetInt(y);
        graf[x].push_back(y);
        graf[y].push_back(x);
    }
    l = r = 1;
    DFS(1, l);
    for (i = 1; i <= n; i++) viz[i] = false, dist[i] = 0;
    viz[l] = true;
    maxi = 0;
    DFS(l, r);
    fout << dist[r] + 1;

    return 0;
}