def sieve(n):
    res = []
    is_prime = [True] * (n + 1)
    
    for i in xrange(2, n + 1):
        if is_prime[i]:
            res.append(i)

            for j in xrange(i * i, n + 1, i):
                is_prime[j] = False

    return res

def ng(need, numbers):
    for d in numbers:
        if not need[d]:
            return True
        
    return False

def ok(need, exist):
    for n, e in zip(need, exist):
        if n and not e:
            return False

    return True

primes = sieve(5000000)
n = input()
need = [False] * 10

for a in map(int, raw_input().split()):
    need[a] = True

ans = -1
prev = 1

l = 0
while l < len(primes):
    r = l
    exist = [False] * 10

    while r < len(primes):
        numbers = map(int, str(primes[r]))

        if ng(need, numbers):
            break

        for d in numbers:
            exist[d] = True

        r += 1

    current = primes[r] - 1 if r < len(primes) else 5000000
    if ok(need, exist):
        diff = current - prev
        ans = max(ans, diff)
        
    prev = current + 2
    l = r + 1

print ans