#include <fstream>
#include <vector>
#include <queue>
#include <cstring>
#define nmax 100002
using namespace std;
ifstream fin("darb.in");
ofstream fout("darb.out");

vector <int> graf[nmax];
int v[nmax],x,y,n,diametru,ultimul;
int viz[nmax];
queue <int> coada;

void bfs(int nod)
{
    memset(v,0,nmax);
    memset(viz,0,nmax);
    viz[nod]=1;
    v[nod]=1;
    coada.push(nod);
    while(!coada.empty())
    {
        int nod=coada.front();
        coada.pop();
        for(int i=0;i<graf[nod].size();i++)
        {
            if(!viz[graf[nod][i]])
            {
                viz[graf[nod][i]]=1;
                v[graf[nod][i]]=v[nod]+1;
                diametru=v[graf[nod][i]];
                ultimul=graf[nod][i];
                coada.push(graf[nod][i]);
            }
        }
    }
}

int main()
{
    fin>>n;
    fin>>x>>y;
    while(!fin.eof())
    {
        graf[x].push_back(y);
        graf[y].push_back(x);
        fin>>x>>y;
    }
    bfs(1);
    bfs(ultimul);
    fout<<diametru;
    return 0;
}