#include <iostream>
#include <vector>
#include <random>
#include <algorithm>
using ll = long long;
using LL = __int128_t;
std::mt19937 mt{1};
ll power(const LL a, const LL n, const ll mod) { return n == 0 ? 1 : n % 2 == 1 ? power(a, n - 1, mod) * a % mod : power(a * a % mod, n / 2, mod); }
bool MillerRabin(const ll n, const int rep = 2)
{
    if (n == 1) return false;
    ll s = 0, d = n - 1;
    for (; d % 2 == 0; s++, d /= 2) {}
    std::uniform_int_distribution<ll> dist{1, n - 1};
    for (int i = 0; i < rep; i++) {
        const ll a = dist(mt);
        if (power(a, n - 1, n) != 1) { return false; }
        ll num = power(a, d, n);
        if (num == 1) { continue; }
        bool comp = true;
        for (ll r = 0; r < s; r++) {
            if (num == n - 1) {
                comp = false;
                break;
            }
            num = (LL)num * (LL)num % n;
        }
        if (comp) { return false; }
    }
    return true;
}

int main()
{
    int N;
    std::cin >> N;
    std::vector<std::string> A(N);
    for (int i = 0; i < N; i++) { std::cin >> A[i]; }
    ll ans = -1;
    do {
        std::string s;
        for (const auto& e : A) { s += e; }
        const ll p = std::stoll(s);
        if (MillerRabin(p)) { ans = std::max(ans, p); }
    } while (std::next_permutation(A.begin(), A.end()));
    std::cout << ans << std::endl;
    return 0;
}