#include <iostream>
#include <vector>
#include <algorithm>

using ll = long long;

bool is_prime(ll x) {
    if (x <= 1) {
        return false;
    }
    for (ll i = 2; i * i <= x; i++) {
        if (x % i == 0) {
            return false;
        }
    }
    return true;
}

ll gcd(ll a, ll b) {
    if (b == 0) {
        return a;
    }
    return gcd(b, a % b);
}

int main() {
    int n;
    std::cin >> n;
    std::vector<ll> a_(n);
    for (int i = 0; i < n; i++) {
        std::cin >> a_[i];
    }
    std::vector<ll> a;
    for (int i = 0; i < 10; i++) {
        if (std::count(a_.begin(), a_.end(), i) == 0) {
            a.push_back(i);
        }
    }

    ll d = 0;
    for (int i = 0; i < a.size(); i++) {
        d = gcd(d, a[i]);
    }

    if (d != 1) {
        if (!is_prime(d) || std::count(a.begin(), a.end(), d) == 0) {
            std::cout << -1 << std::endl;
        }
        else {
            std::cout << d << std::endl;
        }
        return 0;
    }

    ll len = 0;
    ll k = a.size();
    while (true) {
        ll max = 1;
        for (int i = 0; i < len; i++) {
            max *= k;
        }
        for (int i = 0; i < max; i++) {
            ll j = i, x = 0;
            for (int l = 0; l < len; l++) {
                x *= 10;
                x += a[j % k];
                j /= k;
            }

            if (is_prime(x)) {
                std::cout << x << std::endl;
                return 0;
            }
        }
        len++;
    }
}