// yukicoder: No.12 限定された素数
// 2019.4.12 bal4u

#include <stdio.h>
#include <ctype.h>

#define MAX  5000000
#define SQRT 2236
char notPrime[MAX] = { 1,1,0,0,1 };			// zero: if prime
int ptbl[350000] = { 2, 3, 5, 7 };
#define LIM 348513
int pbit[350000] = { 4, 8, 32, 128 };
int bit[10];

int getBit(int k)
{
	int res = 0;
	while (k) res |= bit[k % 10], k /= 10;
	return res;
}
void sieve()
{
	int i, j;
	for (i = 3; i <= SQRT; i += 2) if (!notPrime[i]) {
		for (j = i * i; j < MAX; j += i) notPrime[j] = 1;
	}
	j = 4; for (i = 9; i <= MAX; i += 2) if (!notPrime[i]) {
		ptbl[j] = i, pbit[j++] = getBit(i);
	}
}

int main()
{
	int i, N, fr, a, mask, ans;

	for (i = 0; i < 10; i++) bit[i] = 1 << i;
	sieve();
	scanf("%d", &N);
	if (N == 10) { puts("4999999"); return 0; }
	mask = 0; for (i = 0; i < N; i++) {
		scanf("%d", &a), mask |= bit[a];
	}

	ans = -1, fr = 0, a = 0;
	for (i = 0; i < LIM; i++) {
		if ((mask | pbit[i]) == mask) a |= pbit[i];
		else {
			if (a == mask && ptbl[i] - fr - 2 > ans) ans = ptbl[i] - fr - 2;
			fr = ptbl[i], a = 0;
		}
	}
	printf("%d\n", ans);
	return 0;
}