#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define itn int
#define rep2(i,a,n) for(int i = (a);i < (n);i++)
#define rep(i,n) rep2(i,0,n)
using P = pair<int,int>;

int main(void){
    int ans[11] = {};
    for(int i = 0;i < 9;i++){
        int b;
        cin >> b;
        ans[b]++;
    }
    
    for(int i = 1;i < 11;i++){
        if(ans[i] == 0)cout << i << endl;
    }
}