#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(),x.end()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
template<class T> inline bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T> inline bool chmin(T&a,T b){if(a>b){a=b;return 1;}return 0;}
using ll = long long;

int a[10],b[10];

int main(){
    rep(i,9) cin >> b[i], a[b[i]-1]++;
    rep(i,10)if(!a[i]) cout << i+1 << endl;
}