#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <utility>

using namespace std;

int main(void){

    vector<int> b(9);
    for(int i = 0; i < 9; i++) cin >> b[i];
    sort(b.begin(), b.end());
    for(int i = 0; i < 9; i++){
        if(b[i] != i + 1){
            cout << i + 1 << endl;
            return 0;
        }
    }
    cout << 10 << endl;

    return 0;
}