#!/usr/bin/ python3.8
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines


N = int(readline())
A = map(int, read().split())

full = 0
for x in A:
    full += (1 << x)


def num_to_set(n):
    x = 0
    while n:
        n, r = divmod(n, 10)
        x |= (1 << r)
    return x


U = 5 * 10 ** 6 + 1
is_prime = [0] * U
is_prime[2] = 1
for n in range(3, U, 2):
    is_prime[n] = 1
for p in range(3, U, 2):
    if p * p >= U:
        break
    if is_prime[p]:
        for i in range(p * p, U, p + p):
            is_prime[i] = 0

ng = []
ok = []
for p in range(U):
    if is_prime[p]:
        s = num_to_set(p)
        if s & (~full):
            ng.append(p)
        else:
            ok.append((p, s))

ng.append(U)
ok.append((U, 0))
L = 1
i = 0
answer = -1
for x in ng:
    R = x - 1
    se = 0
    while True:
        p, s = ok[i]
        if p > R:
            break
        se |= s
        i += 1
    if se == full and answer < R - L:
        answer = R - L
    L = x + 1

print(answer)