// #pragma GCC optimize("O3")
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include <bits/stdc++.h>
using namespace std;

#define PB emplace_back
// #define int long long
#define ll long long
#define vi vector<int>
#define siz(a) ((int) ((a).size()))
#define rep(i, a, b) for (int i = (a); i <= (b); ++i)
#define per(i, a, b) for (int i = (a); i >= (b); --i)
void print(vi n) {rep(i, 0, siz(n) - 1) cerr << n[i] << " \n"[i == siz(n) - 1];}

const int N = 1e7;
int a, s[10];
int mu[N + 5], pm[N + 5], phi[N + 5], top;
bool vis[N + 5];
void sieve() {
	mu[1] = phi[1] = 1;
	rep(i, 2, N) {
		if(!vis[i]) pm[++top] = i, mu[i] = -1, phi[i] = i - 1;
		for(int j = 1; j <= top && i * pm[j] <= N; ++j) {
			vis[i * pm[j]] = 1;
			if(i % pm[j] == 0) {
				phi[i * pm[j]] = phi[i] * pm[j];
				break;
			}
			phi[i * pm[j]] = phi[i] * (pm[j] - 1);
			mu[i * pm[j]] = -mu[i];
		}
	}
}

signed main() {
	// freopen(".in", "r", stdin);
	// freopen(".out", "w", stdout);
	ios::sync_with_stdio(0);
	cin.tie(0), cout.tie(0);
	sieve();
	cin >> a;
	int x;
	rep(i, 1, a) {
		cin >> x;
		s[x] = 1;
	}
	rep(i, 2, N) if(!vis[i]) {
		int x = i;
		bool ans = 1;
		rep(j, 1, 10) {
			if(!x) break;
			ans &= !s[x % 10];
			x /= 10;
		}
		if(ans) return cout << i, 0;
	}
	cout << -1;
	return cerr << endl << 1.0 * clock() / CLOCKS_PER_SEC << endl, 0;
}