#include <bits/stdc++.h>

using namespace std;

vector<bool> sieve(int n) {
	vector<bool> is_prime(n + 1, true);
	is_prime[0] = false;
	is_prime[1] = false;
	for (int i = 2; i <= n; i++) {
		if (!is_prime[i]) continue;
		for (int j = 2 * i; j <= n; j += i) is_prime[j] = false;
	}
	return is_prime;
}

void change(int x, int* used, int c) {
	used[x % 10] += c;
	int tmp = 10;
	while (x >= tmp) {
		used[x / tmp % 10] += c;
		tmp *= 10;
	}
}

bool check1(int* used, bool* memo) {
	bool res = false;
	for (int i = 0; i < 10; i++) {
		if (memo[i] || used[i] == 0) continue;
		res = true;
		break;
	}
	return res;
}

bool check2(int* used, bool* memo) {
	bool res = true;
	for (int i = 0; i < 10; i++) {
		if (memo[i] == (used[i] != 0)) continue;
		res = false;
		break; 
	}
	return res;
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N;
	cin >> N;
	bool memo[10] = {};
	for (int i = 0; i < N; i++) {
		int A;
		cin >> A;
		memo[A] = true;
	}

	vector<bool> p(sieve(5000000));
	int used[10] = {};
	int ans = -1;
	for (int K = 1, L = 1; L <= 5000000; L++) {
		if (p[L]) change(L, used, 1);
		if (check1(used, memo)) {
			while (K < L) {
				if (p[K]) change(K, used, -1);
				K++;
				if (!check1(used, memo)) break;
			}
		}
		if (check2(used, memo)) {
			ans = max(ans, L - K);
		}
	}
	cout << ans << endl;
	return 0;
}