#include <bits/stdc++.h>
using namespace std;

vector < vector <int>> graf;
int maxi=0,maxi_csucs=0;

void dfs(int p, int mely){
    if(mely > maxi){
        maxi = mely;
        maxi_csucs = p;
    }
    for(int x : graf[p]){
        dfs(x, mely + 1);
    }
}

int main() {
	int n; cin >> n;
    graf.resize(n+1);
    vector <bool> bejovo(n+1,0);
    int a = 0,b;
    for(int i = 0; i < n; i++){
        cin >> a >> b;
        graf[a].push_back(b);
        bejovo[b] = 1;
    }
    int gyoker = 0;
    for(int i = 1; i <= n; i++){
        if(!bejovo[i]){
            gyoker = i;
        }
    }
    dfs(gyoker, 0);
    cout << maxi_csucs;
}