#include<bits/stdc++.h>

int main(){
    using namespace std;
    constexpr unsigned long MOD{1000000007};
    unsigned long N;
    cin >> N;
    vector<unsigned long> A(N);
    for(auto&& i : A)cin >> i;
    if(any_of(begin(A), end(A), [](const auto& i){return i == 0;}))return 0 & puts("-1");
    if(any_of(begin(A), end(A), [](const auto& i){return i >= 4;}))return 0 & puts("1000000007");
    unsigned long ans{1};
    for(const auto& i : A){
        for(unsigned long j{[](const auto& x){unsigned long ret{1}; for(unsigned long i{1}; i <= x; ++i)ret *= i;return ret;}(i)}; j--; )ans *= i;
        if(ans > MOD)return 0 & puts("1000000007");
    }
    cout << MOD % ans << endl;
    return 0;
}