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

int main()
{
    set<int> B;
    for (int i = 0; i < 9; ++i){
        int a;
        cin >> a;
        B.insert(a);
    }

    for (int i = 1; i <= 10; ++i){
        auto search = B.find(i);
        if (search == B.end()){
            cout << i << endl;
        }
    }
    
    return 0;
}