#include <fstream>
#include <vector>
using namespace std;

ifstream fin("darb.in");
ofstream fout("darb.out");
const int Vmax = 100001;
vector<int> v[Vmax];
int lenMax[Vmax];
int sol;
void dfs(int nod, int father){
    int min1=0, min2=0;
    for(int j : v[nod]){
        if(j!=father){
            dfs(j, nod);
            if(lenMax[j]>min1){
                min2=min1;
                min1=lenMax[j];
            }
            else if(lenMax[j]>min2){
                min2=lenMax[j];
            }
        }
    }
    sol=max(sol, min1+min2+1);
    lenMax[nod] = min1+1;
}

int main(){
    int n;
    fin>>n;
    int n1=n;
    while(n1--){
        int x, y;
        fin>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    dfs(1, 0);
    fout<<sol;
}