#include<iostream>
#include<vector>
#include<map>
#include<set>
using namespace std;

int main(){
    set<string> a;
    set<string> b;
    vector<string> v;
    int n;
    cin >> n;
    for(int i = 0; i < n; i++){
        string x, y;
        cin >> x >> y;
        if(a.count(x)==0&&b.count(x)==0)    v.push_back(x);
        if(a.count(y)==0&&b.count(y)==0)    v.push_back(y);
        a.insert(x);
        b.insert(y);
    }
    for(string s : v)   if(a.count(s)==0)   cout << s << endl;
    return 0;
}