n = int(input())

a = [False] * 10
for x in map(int, input().split()):
    a[x] = True

sieve = [True] * 5000002
ans = -1
k = 1
d = [False] * 10
for p in range(2, 5000002):
    if sieve[p] or p == 5000001:
        for i in range(p * p, 5000002, p):
            sieve[i] = False
        if p < 5000001:
            ok = True
            for x in map(int, str(p)):
                if not a[x]:
                    ok = False
                    break
        if not ok or p == 5000001:
            for i in range(10):
                if a[i] != d[i]:
                    break
            else:
                ans = max(ans, p - 1 - k)
            k = p + 1
        else:
            for x in map(int, str(p)):
                d[x] = True
print(ans)