def prime_sieve(n):
    is_prime = [True for i in range(n + 1)]
    is_prime[0] = False
    is_prime[1] = False
    for i in range(4, n + 1, 2):
        is_prime[i] = False
    for i in range(3, int(n**0.5 + 1), 2):
        if is_prime[i]:
            for j in range(i * i, n + 1, i):
                is_prime[j] = False
    return [i for i in range(n + 1) if is_prime[i]]


def using_digits(n, base=10):
    digits = []
    while n > 0:
        digits.append(n % base)
        n //= base
    return digits

N = int(input())
A = list(map(int, input().split()))
if A == [2]:
    print(1)

primes = [1] + prime_sieve(5000000) + [5000000]
length_primes = len(primes)

digits = [using_digits(p) for p in primes]
digits_count = [0 for i in range(10)]
max_gap = 0
l = 1
r = 1
while r < length_primes:
    ds = using_digits(primes[r])
    if all(d in A for d in ds):
        for d in ds:
            digits_count[d] += 1
        if all(digits_count[a] > 0 for a in A):
            max_gap = max(max_gap, primes[r + 1] - primes[l - 1] - 3)
    else:
        l = r
        digits_count = [0] * 10
    r += 1
print(max_gap)