def generate_primes(limit):
    is_prime = [0] * (limit + 1)
    primes = []
    for i in range(2, limit + 1):
        if not is_prime[i]:
            primes.append(i)
        for prime in primes:
            if prime * i > limit:
                break
            is_prime[prime * i] = 1
            if i % prime == 0:
                break
    return primes
input()
digits = set(input().split())
current_digits = set()
max_length, last_prime = -1, 1
for prime in generate_primes(5000000):
    prime_digits = set(str(prime))
    if len(prime_digits - digits) > 0:
        if len(digits) == len(current_digits):
            max_length = max(max_length, prime - 1 - last_prime)
        current_digits = set()
        last_prime = prime + 1
    else:
        current_digits |= prime_digits
if len(digits) == len(current_digits):
    max_length = max(max_length, 5000000 - last_prime)
print(max_length)