import itertools
import random

def is_prime(n: int, k: int = 25) -> bool:
    assert(n >= 0)
    if n == 2: return True
    if n < 2 or n & 1 == 0: return False

    d = n - 1
    while d & 1 == 0:
        d >>= 1

    for i in range(k):
        a = random.randint(1, n - 1)
        t = d
        y = pow(a, t, n)
        while t != n - 1 and y != 1 and y != n - 1:
            y = pow(y, 2, n)
            t <<= 1
        if y != n - 1 and t & 1 == 0:
            return False
    return True

if __name__ == '__main__':
    n = int(input())
    a = map(int, input().split())
    ans = -1
    used = set()
    for p in itertools.permutations(a):
        num = int(''.join(map(str, p)))
        if num in used:
            continue
        used.add(num)
        if is_prime(num):
            ans = max(ans, num)
    print(ans)