#include <algorithm>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

using namespace std;

typedef long long ll;

#define MOD 1000000007

int main() {
  int sum = 10 * 11 / 2;
  for (int i = 0; i < 9; ++i) {
    int b;
    cin >> b;
    sum -= b;
  }
  cout << sum << endl;
  return 0;
}