#include <bits/stdc++.h>
//#include <chrono>
//#pragma GCC optimize("Ofast")
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()
#define fi first
#define se second

using ll = long long;
using vec = vector<ll>;
using mat = vector<vec>;

ll N,M,H,W,Q,K,A,B;
string S;
typedef pair<ll, ll> P;
const ll INF = (1LL<<58);

int main() {
    cin>>N;
    vec a(N);
    rep(i, N) cin>>a[i];
    const ll inf = (ll)(1e+9 + 7);
    if(*min_element(ALL(a)) == 0){
        cout<<-1<<endl;
    }else if(*max_element(ALL(a)) >= 4){
        cout<<inf<<endl;
    }else{
        ll res(1);
        rep(i, N){
            ll fact(1);
            rep(j, a[i]) fact *= j + 1;
            rep(j, fact){
                if((res *= a[i]) > inf){
                    cout<<inf<<endl;
                    return 0;
                }
            }
        }
        cout<<inf % res<<endl;
    }
}