import random
import itertools

def suspect(a, e, k, n):
    a = pow(a, e, n)
    if a == 1: return True
    for _ in range(k):
        if a == n - 1: return True
        a = a * a % n
    return False

def isprime(n):
    if n <= 1 or (n > 2 and n % 2 == 0): return False
    e = n - 1
    k = 0
    while e % 2 == 0:
        e //= 2
        k += 1
    for _ in range(3):
        b = random.randint(2, n - 2)
        if not suspect(b, e, k, n): return False
    return True

n = int(input())
a = map(int, input().split())

ans = -1

for p in itertools.permutations(a):
    x = ''
    for e in p:
        x += str(e)
    x = int(x)
    if isprime(x):
        ans = max(ans, x)
print(ans)