#include <cstdio>
#include <vector>
#include <utility>
#include <algorithm>
using namespace std;

#define MAX 5000000
#define N_MAX 10

int N;
int A[N_MAX];
bool isnotprime[MAX + 1];
vector<pair<int, int>> prime;

void make_prime() {
	isnotprime[0] = isnotprime[1] = 1;
	for (int i = 2; i * i <= MAX; i++) {
		if (!isnotprime[i]) {
			for (int j = i * i; j <= MAX; j += i) {
				isnotprime[j] = 1;
			}
		}
	}
	prime.emplace_back(-1, 0);
	for (int i = 2; i <= MAX; i++) {
		if (isnotprime[i]) continue;
		prime.emplace_back(i, 0);
	}
	prime.emplace_back(MAX, 0);
}

void make_mask() {
	for (int i = 1; i + 1 < prime.size(); i++) {
		int x = prime[i].first;
		int mask = 0;
		while (x) {
			mask |= 1 << x % 10;
			x /= 10;
		}
		prime[i].second = mask;
	}
}

int main() {
	make_prime();
	make_mask();
	
	scanf("%d", &N);
	for (int i = 0; i < N; i++) scanf("%d", A + i);
	
	if (N == 10) {
		printf("%d\n", MAX - 1);
		return 0;
	}
	
	int mask = 0;
	for (int i = 0; i < N; i++) mask |= 1 << A[i];
	
	int res = -1;
	for (int i = 1; i + 1 < prime.size(); i++) {
		int bit = 0;
		for (int j = i; j + 1 < prime.size(); j++) {
			bit |= prime[j].second;
			if ((bit | mask) != mask) break;
			if (bit == mask) {
				res = max(res, (prime[j + 1].first - 1) - (prime[i - 1].first + 1));
			}
		}
	}
	
	printf("%d\n", res);
	
	return 0;
}