#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
const double PI = acos(-1);
const ll MOD = 1000000007;
using Graph = vector<vector<int>>;

int main() {
  int N; cin >> N;
  vector<ll> P(N);
  rep(i,N) cin >> P[i];
  
  ll ans = 1;
  rep(i,N) {
    ans *= P[i];
    while (ans >= 10) {
      ll p = ans;
      ans = 0;
      while (p != 0) {
        ans += p % 10;
        p /= 10;
      }
    }
  }

  cout << ans << endl;
}