#include<iostream>
#include<vector>
#include<queue>
#include<fstream>
using namespace std;
ifstream f("darb.in");
ofstream g("darb.out");
queue <int> q;
vector <int> g[100001];
int sol[100001];
bool v[100001];
void BFS(int x,bool b,queue <int> &bfs)
{
    int z,i;
    v[x]=true;
    bfs.push(x);
    q.push(x);
    while(!q.empty())
    {
        z = q.front();
        q.pop();
        for(i=0;i<g[z].size();i++)
        {
            if(!v[g[z][i]])
            {
                bfs.push(g[z][i]);
                q.push(g[z][i]);
                v[g[z][i]] = true;
                if(b)
                    sol[g[z][i]] = sol[z] + 1;
            }
        }
    }
}
int main()
{
    int n;
    int a,b;
    int i;
    fstream f("darb.in",ios::in);
    f>>n;
    while(f>>a>>b)
    {
        g[a].push_back(b);
        g[b].push_back(a);
    }

    queue <int> bfs1,bfs2;
    BFS(1,false,bfs1);
    int x;
    x = bfs1.back();
    for(i=1;i<=n;i++)
        v[i] = false;
    BFS(x,true,bfs2);
    int maxim = 0;
    for(int i=1;i<=n;i++)
        if(sol[i]>maxim)
            maxim=sol[i];
    maxim=maxim+1;
    g<<maxim;

}