#include <fstream>
#include <iostream>
#include <vector>
#include <queue>
#include <cstring>
using namespace std;
#define DIM 100005
vector <int> vf[DIM];
queue <int> q;
int viz[DIM], dist[DIM], grad[DIM];
int nr_vf, capat;

void citeste()
{
    ifstream f("darb.in");
    f>>nr_vf;
    int x, y;
    for(int i = 0; i < nr_vf-1; i++)
    {
        f>>x>>y;
        vf[x].push_back(y);
        vf[y].push_back(x);
        grad[x]++;
        grad[y]++;
    }
}
int isArb()
{
    int s = 0;
    for(int i = 1; i <= nr_vf; i++)
        s+=grad[i];
    if(s!=2*(nr_vf-1))
        return 0;
    return 1;
}
void bf(int start)
{
    memset(viz, 0, DIM*sizeof(int));
    memset(dist, 0, DIM*sizeof(int));
    int nod;
    q.push(start);
    dist[start] = 1;
    while(!q.empty())
    {
        nod = q.front();
        viz[nod] = 1;
        for(unsigned int i = 0; i < vf[nod].size(); i++)
            if(!viz[vf[nod][i]])
            {
                viz[vf[nod][i]] = 1;
                q.push(vf[nod][i]);
                dist[vf[nod][i]] = dist[nod]+1;
                capat = vf[nod][i];
            }
        q.pop();
    }
}
int main()
{
    citeste();
    if(!isArb())
    {
        cout<<"Nu e arbore";
        return 0;
    }
    bf(1);
    bf(capat);
    ofstream g("darb.out");
    g<<dist[capat];
    return 0;
}