#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int f[11] = {};
    rep(i,9){
        int b; cin >> b;
        f[b]++;
    }
    srep(i,1,11){
        if(f[i] == 0){
            cout << i << endl;
        }
    }
    return 0;
}