#include <algorithm>
#include <iostream>

using namespace std;

int N;
int a, A;
int NP;
int primes[5000000], masks[5000000];
bool is_prime[5000001];

int main() {
	cin >> N;
	for (int i = 0; i < N; i++) {
		cin >> a;
		A |= (1 << a);
	}
	primes[NP] = 0;
	masks[NP++] = (1 << 11) - 1;
	for (int i = 2; i <= 5000000; i++) {
		is_prime[i] = true;
	}
	for (int i = 2; i <= 5000000; i++) {
		if (is_prime[i]) {
			for (int j = i + i; j <= 5000000; j += i) {
				is_prime[j] = false;
			}
			primes[NP] = i;
			int n = i;
			while (n > 0) {
				masks[NP] |= (1 << (n % 10));
				n /= 10;
			}
			NP++;
		}
	}
	primes[NP] = 5000001;
	masks[NP++] = (1 << 11) - 1;
	int res = -1;
	for (int i = 1; i < NP; i++) {
		int mask = 0;
		for (int j = i; j < NP; j++) {
			if (masks[j] & (~A)) {
				if (mask == A) {
					res = max(res, (primes[j] - 1) - (primes[i - 1] + 1));
				}
				i = j;
				break;
			} else {
				mask |= masks[j];
			}
		}
	}
	cout << res << endl;
	return 0;
}