#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a[i];
  constexpr ll m = 1'000'000'007;
  if (*min_element(a.begin(), a.end()) == 0) {
    cout << -1 << '\n';
  }
  else if (*max_element(a.begin(), a.end()) >= 4) {
    cout << m << '\n';
  }
  else {
    ll p = 1;
    rep(i, n) {
      if (a[i] == 1) p *= 1;
      if (a[i] == 2) p *= 2 * 2;
      if (a[i] == 3) p *= 3 * 3 * 3 * 3 * 3 * 3;
      if (p > m) {
        cout << m << '\n';
        return 0;
      }
    }
    cout << m % p << '\n';
  }
  return 0;
}