#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

const int MOD=1e9+7;

int main(){
  int n;
  cin>>n;
  
  vector<int> A(5);
  rep(i,n){
    int x;
    cin>>x;
    if(x>3) A[4]++;
    else A[x]++;
  }
  
  ll ans=1;
  if(A[0]>0){
    cout<<-1<<endl;
    return 0;
  }
  else if(A[4]>0){
    cout<<MOD<<endl;
    return 0;
  }
  else{
    rep(i,A[3]){
      ans*=729;
      if(ans>MOD){
        cout<<MOD<<endl;
        return 0;
      }
    }
    rep(i,A[2]){
      ans*=4;
      if(ans>MOD){
        cout<<MOD<<endl;
        return 0;
      }
    }
  }
  cout<<MOD%ans<<endl;
  
  return 0;
}