#include <bits/stdc++.h>
using namespace std;
int main(){
    const int MOD = 1e9 + 7;
    int n; cin >> n;
    bool big = false;
    long long rem = 1;
    for(int i = 0; i < n; i++){
        int a; cin >> a;
        if(a == 0){
            cout << -1 << endl;
            return 0;
        }else if(a >= 4){
            big = true;
        }else{
            int f = 1;
            for(int j = 1; j <= a; j++){
                f *= j;
            }
            for(int j = 0; j < f; j++){
                rem *= a;
            }
            if(rem > MOD){
                big = true;
            }
        }
    }
    if(big) cout << MOD << endl;
    else cout << MOD % rem << endl;
    return 0;
}