#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <queue>
#include <bitset>
#include <stack>
#include <functional>

// AtCoder
// #include <atcoder/all>
// using namespace atcoder;

#ifdef LOCAL
    #define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
    #define eprintf(...)
#endif

#define rep_(i, a_, b_, a, b, ...) for (int i = (a), i##_len = (b); i < i##_len; ++i)
#define rep(i, ...) rep_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define reprev_(i, a_, b_, a, b, ...) for (int i = (b-1), i##_min = (a); i >= i##_min; --i)
#define reprev(i, ...) reprev_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define all(x) (x).begin(), (x).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; }
#define fls(x) (64 - __builtin_clzll(x))
#define pcnt(x) __builtin_popcountll(x)
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair <int,int> P;
typedef long double ld;

constexpr int MOD = 1000000007;

int main (void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    ll n; cin >> n;
    ll x = 1;
    rep (i, n) {
        ll a; cin >> a;
        if (a >= 4) {
            cout << MOD << "\n";
            return 0;
        } else if (a == 0) {
            cout << -1 << "\n";
        } else if (a == 2) {
            x *= 4;
        } else if (a == 3) {
            x *= 729;
        }
        if (x > MOD) {
            cout << MOD << "\n";
            return 0;
        }
    }
    cout << MOD % x << "\n";

    /***************************************************/
    /* Use "submit code (with ACL v1)" when using ACL! */
    /***************************************************/
    return 0;
}