#include <iostream>
#include <string>
#include <vector>
using namespace std;

int sumdig(int N) {
  int dig, sum = 0;
  while (N) {
    dig = N % 10;
    sum += dig;
    N /= 10;
  }
  return sum;
}
int main() {
  int N;
  cin >> N;
  int P;
  int sum = 1;
  for (int i = 0; i < N; i++) {
    cin >> P;
    sum *= P;
  }
  int ans = 0;
  while (1) {
    ans = sumdig(sum);
    sum = ans;
    if (ans <= 9) {
      cout << ans << endl;
      return 0;
    }
  }
}