import itertools
import random


def is_prime(n):
    """https://qiita.com/srtk86/items/609737d50c9ef5f5dc59 から拝借しています。"""
    if n == 2: return True
    if n == 1 or n & 1 == 0: return False

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

    for k in range(100):
        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 = (y * y) % n
            t <<= 1

        if y != n - 1 and t & 1 == 0:
            return False

    return True


N = int(input())
A = tuple(map(int, input().split()))
max_prime = -1
for t in set(itertools.permutations(A)):
    x = int("".join(map(str, t)))
    if max_prime < x and is_prime(x):
        max_prime = x
print(max_prime)