#include<bits/stdc++.h>
using namespace std;
#define in f
#define out g

ifstream f ("darb.in");
ofstream g ("darb.out");

queue <int> q;
vector <int> v[1000010];
int n;
int depth[1000010];
int s;
int viz[100010];
int node;
int m;
int x;
int y;
int aux;
int aux1;
int aux2;

int main() {

    in >> n;
    for(int i = 1; i < n; i++) {
        in >> x;
        in >> y;
        v[x].push_back(y);
    }
    q.push(1);
    viz[1] = 1;
    while(q.empty() == false) {
        node = q.front();
        q.pop();
        for(int i = 0; i < v[node].size(); i++) {
            if(viz[v[node][i]] == 0) {
                q.push(v[node][i]);
                depth[v[node][i]] = depth[node] + 1;
                viz[v[node][i]]++;
            }
        }
    }
    for(int i = 1; i <= n; i++) {
        if(depth[i] > aux) {
            aux2 = i;
        }
        aux = max(aux, depth[i]);
    }
    depth[aux2] = 0;
    for(int i = 1; i <= n; i++) {
        aux1 = max(aux1, depth[i]);
    }
    out << aux1 + aux + 1;
}