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

template <typename T>
T gcd(T a, T b)
{
	while (b)
	{
		T tmp = b;
		b = a % b;
		a = tmp;
	}
	return a;
}

template <typename T>
T pow_mod(T a, T n, T mod)
{
	T r = 1;
	for (; n; n >>= 1)
	{
		if (n & 1)
		{
			(r *= a) %= mod;
		}
		(a *= a) %= mod;
	}
	return r;
}

template <typename T>
bool miller_rabin(T n)
{
	if (n < 2)
	{
		return false;
	}
	for (T a = 2; a < min(T(100), n); a++)
	{
		if (gcd(a, n) != 1)
		{
			continue;
		}
		T m = n - 1;
		if (pow_mod(a, m, n) != 1)
		{
			return false;
		}
		for (m >>= 1; m % 2 == 0; m >>= 1)
		{
			T puni = pow_mod(a, m, n);
			if (puni == n - 1)
			{
				break;
			}
			if (puni != 1)
			{
				return false;
			}
		}
		T puni = pow_mod(a, m, n);
		if ((puni != n - 1) && (puni != 1))
		{
			return false;
		}
	}
	return true;
}

int main()
{
	int n;
	cin >> n;
	vector<int> as(n);
	for (auto &a : as)
	{
		cin >> a;
	}
	int64_t ans = -1;
	do
	{
		string s = "";
		for (auto &a : as)
		{
			s += to_string(a);
		}
		__int128_t x = 0;
		for (auto &c : s)
		{
			x *= 10;
			x += c - '0';
		}
		if (miller_rabin(x))
		{
			ans = max(ans, int64_t(x));
		}
	} while (next_permutation(as.begin(), as.end()));
	cout << ans << endl;
	return 0;
}