#include <iostream>
#include <vector>
#include <fstream>

#define NMAX 100010
using namespace std;
ifstream fin("darb.in");
ofstream fout("darb.out");
int n, m, s;
int viz[NMAX];
vector<int>G[NMAX];

void citire();
void bfs();
void zero();
int main()
{
    citire();
    bfs();
    return 0;
}
void bfs()
{
    int prim = 0, ultim = 0, i, x;
    int coada[NMAX];
    coada[prim] = 1;
    viz[1] = 1;
    while(prim <= ultim)
    {
        x = coada[prim++];
        //fout<<x<<' ';
        for(i = 0; i < G[x].size(); i++)
            if(!viz[G[x][i]])
            {
                viz[G[x][i]] = viz[x] + 1;
                coada[++ultim] = G[x][i];
            }
    }
    //cout<<coada[ultim];
    prim=0;
    coada[prim]=coada[ultim];
    ultim=0;
    zero();
    viz[coada[prim]]=1;

    while(prim <= ultim)
    {
        x = coada[prim++];
        //fout<<x<<' ';
        for(i = 0; i < G[x].size(); i++)
            if(!viz[G[x][i]])
            {
                viz[G[x][i]] = viz[x] + 1;
                coada[++ultim] = G[x][i];
            }
    }
    fout<<viz[coada[ultim]]<<'\n';;
}
void citire()
{
    int i, x, y;
    fin >> n;
    for(i = 0; i < n; i++)
    {
        fin >> x >> y;
        //adaugam x in lista de adiacenta a lui y;
        G[y].push_back(x);
        G[x].push_back(y);
    }
}
void zero()
{
   int i;
   for (i=1; i<=n; i++)
      viz[i]=0;
}