def Eratosthenes(n):
    sieve = [True] * ((n + 1) // 2)
    for i in range(1, (int(n ** 0.5) + 1) // 2):
        if sieve[i]:
            for j in range(i * 3 + 1, (n + 1) // 2, i * 2 + 1):
                sieve[j] = False
    res = [i * 2 + 1 for i, s in enumerate(sieve) if s]
    res[0] = 2
    return res


def check(nums, used, n):
    cnt = [0, 0]
    for i in range(10):
        if used[i] > 0:
            cnt[nums[i]] += 1
    if cnt[0] > 0:
        return -1
    if cnt[1] < n:
        return 0
    return 1


def getDigits(x):
    ret = []
    while x > 0:
        ret.append(x % 10)
        x //= 10
    return ret


n = int(input())
a = list(map(int, input().split()))
MAX = 5000000
prime = Eratosthenes(MAX)
nums = [0] * 10
for i in a:
    nums[i] = 1

idx = 0
l = 1
k = 1

ans = -1
state = 0
pre = 0

while idx < len(prime):
    d = []
    state = 0
    used = [0] * 10
    while state != -1:
        pre = state
        k = prime[idx]
        d.clear()
        d = getDigits(k)
        for i in d:
            used[i] += 1
        state = check(nums, used, n)
        idx += 1
        if idx >= len(prime):
            pre = state
            break

    if pre == 1:
        ans = max(ans, k - 1 - l)
    if idx < len(prime):
        l = k + 1

if state == 1:
    ans = max(ans, MAX - l)

print(ans)