#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

int f(long long x) {
  int ret = 0;
  while (x) {
    ret += x % 10;
    x /= 10;
  }
  return ret;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;

  int ret = 1;
  REP (i, n) {
    long long p;
    cin >> p;
    ret *= f(p);
    ret = f(ret);
  }

  while (ret > 10)
    ret = f(ret);

  cout << ret << endl;
  
  return 0;
}