#include <iostream>
using namespace std;

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