def seachPrimeNum(N):
    if N < 2:
        return []
    max = int(N ** 0.5)
    seachList = [i for i in range(3, N + 1, 2)]
    primeNum = [2]
    while seachList[0] <= max:
        primeNum.append(seachList[0])
        tmp = seachList[0]
        seachList = [i for i in seachList if i % tmp != 0]
    primeNum.extend(seachList)
    return primeNum

def conv(x):
    ret = 0
    while x:
        ret |= (1 << x % 10)
        x //= 10
    return ret

PL = seachPrimeNum(5 * 10 ** 6)
NP = len(PL)
PL.append(5 * 10 ** 6 + 1)
l = 1
N = int(input())
A = list(map(int,input().split()))
B = 0
for a in A:
    B |= (1<<a)
NB = ((1<<10)-1) ^ B
ans = 0
tmp = 0
for i in range(NP):
    p = PL[i]
    if conv(p) & NB:
        l = p + 1
        tmp = 0
    else:
        tmp |= conv(p)
        if tmp == B:
            ans = max(ans,PL[i + 1] - 1 - l)
if ans == 0:
    print(-1)
else:
    print(ans)