#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
void Say(bool say, string a = "Yes", string b = "No"){cout << (say ? a : b) << endl;};


int main(){

    vector<ll>v(11, 0);
    for(ll i = 0; i < 9; i++){
        ll b;
        cin >> b;
        v[b] = 1;
    }
    for(ll i = 1; i <= 10; i++){
        if(v[i] == 0){
            cout << i << endl;
        }
    }

    return 0;
}