#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
#include <iterator>
#include <string>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <cassert>
#include <cmath>
#include <ctime>
#include <iomanip>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <bitset>
#include <random>
#include <utility>
#include <functional>
using namespace std;
template<int m> struct modint
{
	private:
	unsigned int value;
	static constexpr int mod() {return m;}

	public:
	constexpr modint(const long long x = 0) noexcept
	{
		long long y = x;
		if(y < 0 || y >= mod())
		{
			y %= mod();
			if(y < 0) y += mod();
		}
		value = (unsigned int)y;
	}
	static constexpr int get_mod() noexcept {return m;}
	static constexpr int primitive_root() noexcept
	{
		assert(m == 998244353);
		return 3;
	}
	constexpr unsigned int val() noexcept {return value;}
	constexpr modint &operator+=(const modint &other) noexcept
	{
		value += other.value;
		if(value >= mod()) value -= mod();
		return *this;
	}
	constexpr modint &operator-=(const modint &other) noexcept
	{
		unsigned int x = value;
		if(x < other.value) x += mod();
		x -= other.value;
		value = x;
		return *this;
	}
	constexpr modint &operator*=(const modint &other) noexcept
	{
		unsigned long long x = value;
		x *= other.value;
		value = (unsigned int) (x % mod());
		return *this;
	}
	constexpr modint &operator/=(const modint &other) noexcept
	{
		return *this *= other.inverse();
	}
	constexpr modint inverse() const noexcept
	{
		assert(value);
		long long a = value,b = mod(),x = 1,y = 0;
		while(b)
		{
			long long q = a/b;
			a -= q*b; swap(a,b);
			x -= q*y; swap(x,y);
		}
		return modint(x);
	}
	constexpr modint power(long long N) const noexcept
	{
		assert(N >= 0);
		modint p = *this,ret = 1;
		while(N)
		{
			if(N & 1) ret *= p;
			p *= p;
			N >>= 1;
		}
		return ret;
	}
	constexpr modint operator+() {return *this;}
	constexpr modint operator-() {return modint() - *this;}
	constexpr modint &operator++(int) noexcept {return *this += 1;}
	constexpr modint &operator--(int) noexcept {return *this -= 1;}
	friend modint operator+(const modint& lhs, const modint& rhs) {return modint(lhs) += rhs;}
	friend modint operator-(const modint& lhs, const modint& rhs) {return modint(lhs) -= rhs;}
	friend modint operator*(const modint& lhs, const modint& rhs) {return modint(lhs) *= rhs;}
	friend modint operator/(const modint& lhs, const modint& rhs) {return modint(lhs) /= rhs;}
	friend ostream &operator<<(ostream &os,const modint &x) {return os << x.value;}
};
/* using mint = modint<998244353>; */
using mint = modint<1000000007>;
vector<pair<long long,int>> PrimeFactorize(long long N)
{
	vector<pair<long long,int>> res;
	for(long long p = 2;p * p <= N;p++)
	{
		if(N % p != 0)
		{
			continue;
		}
		res.push_back(make_pair(p,0));
		while(N % p == 0)
		{
			N /= p;
			res.back().second++;
		}
	}
	
	if(N > 1)
	{
		res.push_back(make_pair(N,1));
	}

	return res;
}

void Main()
{
	int N;
	cin >> N;
	vector<int> A(N);
	for(int i = 0;i < N;i++)
	{
		cin >> A[i];
	}
	bool zero = false;
	for(int i = 0;i < N;i++)
	{
		if(A[i] == 0)
		{
			zero = true;
		}
	}
	if(zero)
	{
		cout << "-1\n";
	}
	else
	{
		for(int i = 0;i < N;i++)
		{
			if(A[i] >= 4)
			{
				cout << (int)1e9 + 7 << "\n";
				return;
			}
		}
		vector<int> cnt(4);
		for(int i = 0;i < N;i++)
		{
			cnt[A[i]]++;
		}
		long long p = 1;
		for(int i = 0;i < cnt[2];i++)
		{
			p *= 4;
			if(p > (int)1e9 + 7)
			{
				cout << (int)1e9 + 7 << "\n";
				return;
			}
		}
		for(int i = 0;i < cnt[3];i++)
		{
			p *= 729;
			if(p > (int)1e9 + 7)
			{
				cout << (int)1e9 + 7 << "\n";
				return;
			}
		}
		cout << ((int)1e9 + 7) % p << "\n";
	}
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int tt = 1;
	/* cin >> tt; */
	while(tt--) Main();
}