#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <map>
using namespace std;


int main() {
    map<string, int> words;
    string curr = "";
    while(cin >> curr){
        if(words.find(curr) == words.end()){
            words.insert({curr, 1});
        }else{
            words.at(curr)++;
        }
    }
    map<string, int> :: iterator itr;
    for(itr = words.begin(); itr != words.end(); itr++){
        if(itr->second == 1){
            cout << itr->first << endl;
        }
    }
    return 0;
}