#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (int i = m; i < n; ++i)
#define FORR(i, m, n) for (int i = m; i >= n; --i)
#define ALL(v) (v).begin(),(v).end()
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
const ll INF=1LL<<60;
const int inf=(1<<30)-1;
const int mod=1e9+7;
int dx[8]={1,0,-1,0,-1,-1,1,1};
int dy[8]={0,1,0,-1,-1,1,-1,1};
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n;cin >> n;
    vector<ll> a(n);
    ll mi=inf,mx=-1;
    REP(i,n){
        cin >> a[i];
        chmin(mi,a[i]);
        chmax(mx,a[i]);
    }
    if(mi==0){
        cout << -1 << endl;
        return 0;
    }
    ll m=mod;
    if(mx>=4){
        cout << m << endl;
        return 0;
    }
    vector<ll> fac(4);
    fac[1]=1,fac[2]=2,fac[3]=6;
    ll ans=1;
    REP(i,n){
        ll res=1;
        REP(j,fac[a[i]]){
            res*=a[i];
        }
        if(ans*res>m){
            cout << m << endl;
            return 0;
        }
        ans*=res;
    }
    cout << m%ans << endl;
}