N = int(input())
A = frozenset(map(int, input().split()))


def primes(n):
    is_prime = [True] * (n + 1)
    is_prime[0] = False
    is_prime[1] = False
    for i in range(2, int(n ** 0.5) + 1):
        if not is_prime[i]:
            continue
        for j in range(i * 2, n + 1, i):
            is_prime[j] = False
    return (i for i in range(n + 1) if is_prime[i])


k = 1
st = set()
ans = -1
for l in primes(5000000):
    l_st = {int(x) for x in str(l)}
    if l_st <= A:
        st |= l_st
    else:
        if st == A:
            ans = max(ans, l - 1 - k)
        st = set()
        k = l + 1

if st == A:
    ans = max(ans, 5000000 - k)
print(ans)