#include <bits/stdc++.h>
using namespace std;

int main()
{
  vector<int> vec(9);

  int sum = 0;
  
  for (int i = 0; i < 9; ++i) {
    cin >> vec[i];
    sum += vec[i];
  }

  int total = 0;
  for (int i = 1; i <= 10; ++i) total += i;

  int ans = total - sum;

  cout << ans << "\n";

  return 0;
}