#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

// オーバーフローしないけど、vsでは使えない
ll powMod(__int128 n, ll k, ll mod) {
    if (n == 0)return 0;
    __int128 res = 1;
    while (k) {
        if (k & 1)res = res*n%mod;
        n = n*n%mod;
        k >>= 1;
    }
    return res;
}

bool MillerRabinPrimalityTest(ll n, int precision = 20) {
    static mt19937_64 mt64;
    if (n == 2)return true;
    if (n == 1 || n % 2 == 0)return false;

    ll q = n - 1, k = 0;
    while (!(q & 1)) {
        q >>= 1;
        k++;
    }

    uniform_int_distribution<ll> unirand(1, n - 1);
    for (int i = 0; i < precision; ++i) {
        ll a = unirand(mt64);
        ll aq = powMod(a, q, n);
        if (aq == 1)continue;
        bool flag = true;
        for (int j = 0; j < k; ++j) {
            if (powMod(aq, (1ll << j), n) == n - 1) {
                flag = false;
                break;
            }
        }
        if (flag)return false;
    }

    return true;
}

void solve() {
    int N;
    cin >> N;
    vector<string> S(N);
    rep(i, N) {
        cin >> S[i];
    }

    ll ans = -1;
    sort(all(S));
    do {
        string t = "";
        each(s, S)t += s;
        ll n = stoll(t);
        if (n > ans && MillerRabinPrimalityTest(n)) {
            ans = n;
        }
    } while (next_permutation(all(S)));

    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);
    solve();
    return 0;
}