#include <bits/stdc++.h>

#define lsb(x) (x & (-x))

using ull = unsigned long long;
using ll = long long;

using namespace std;

constexpr int MAXVAL = (int) 1e7;

bool ciur[MAXVAL + 1];

int main() {
#ifdef HOME
    ifstream cin("input.in");
    ofstream cout("output.out");
#endif
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    for (int i = 2; i * i <= MAXVAL; i++) {
        if (ciur[i] == 0) {
            for (int j = i * i; j <= MAXVAL; j += i) {
                ciur[j] = 1;
            }
        }
    }

    int n;
    cin >> n;

    int mask = 0;
    int answer = 2;
    while (n--) {
        int d;
        cin >> d;
        mask |= (1 << d);
    }

    while (answer < MAXVAL) {
        auto Check = [&mask](int val) {
            if (ciur[val]) {
                return false;
            }

            while (val > 0) {
                int d = val % 10;
                val /= 10;
                if (mask & (1 << d)) {
                    return false;
                }
            }
            return true;
        };

        if (Check(answer)) {
            break;
        }
        answer++;
    }

    cout << (answer == MAXVAL ? -1 : answer) << "\n"; 

    return 0;
}