#include <bits/stdc++.h>
#include <fstream>

using namespace std;

int n, maxi1 = -1, maxi2 = -1;

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

void dfs(vector<vector<int>> & adj, vector<int> &viz, int node) {
    for (auto neigh : adj[node]) {
        if (!viz[neigh]) {
            viz[neigh] = viz[node] + 1;
            if (viz[neigh] >= maxi1) {
                maxi2 = maxi1;
                maxi1 = viz[neigh];
            } else if (viz[neigh] >= maxi2) {
                maxi2 = viz[neigh];
            }
            dfs(adj, viz, neigh);
        }
    }
}


int main() {
    in >> n;
    
    vector <vector<int>> adj(n + 1, vector<int>());

    vector<int> viz(n + 1, 0);

    for (int i = 1, x, y; i <= n; i++) {
        in >> x >> y;
        adj[x].push_back(y);
    }

    viz[1] = 0;

    dfs(adj, viz, 1);

    out << maxi1 + maxi2 + 1;
}