#include <iostream>
#include <algorithm>
#include <cstring>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <cmath>

#define AS(a) (sizeof(a)/sizeof(a[0]))
using namespace std;
long long int MOD = 1000000007;
long long int INF = 1000000007;


int main() {
  bool a[10];
  for(int i = 0; i < 10; i++) a[i] = false;

  for(int i = 0; i < 9; i++) {
    int n;
    cin >> n;
    a[n-1] = true;
  }
  for(int i = 0; i < 10; i++) {
    if(!a[i]) {
      cout << (i+1) << endl;
    }
  }

}