#include <bits/stdc++.h>

using namespace std;

#define SZ(x) (int)(x.size())

using ll = long long;
using ld = long double;
using P = pair<int, int>;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;
const double eps = 1e-10;
const int MOD = 1000000007;
const int INF = 1000000000;
const ll LINF = 1ll<<50;

template<typename T>
void printv(const vector<T>& s) {
  for(int i=0;i<(int)(s.size());++i) {
    cout << s[i];
    if(i == (int)(s.size())-1) cout << endl;
    else cout << " ";
  }
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);

  int n; cin >> n;
  ll tmp = 0;
  ll ans = 1;
  for(int i=0;i<n;++i) {
    ll p = 0; cin >> p;
    while(p >= 10) {
      while(p > 0) {
        tmp += p % 10;
        p /= 10;
      }
      p = tmp;
      tmp = 0;
    }
    ans *= p;
    while(ans >= 10) {
      while(ans > 0) {
        tmp += ans % 10;
        ans /= 10;
      }
      ans = tmp;
      tmp = 0;
    }
  }
  cout << ans << endl;
}