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

_, *A = map(int, read().split())
A_str = [str(x) for x in A]


def gen_nums():
    for p in itertools.permutations(A_str):
        yield int(''.join(p))


def MillerRabinTest(n, maxiter=20):
    import random
    if n == 1:
        return False
    elif n == 2:
        return True
    if not n & 1:
        return False

    d = n - 1
    while not (d & 1):
        d >>= 1

    for _ in range(maxiter):
        a = random.randint(1, n - 1)
        t = d
        x = pow(a, t, n)
        while (t != n - 1) and (x != 1) and (x != n - 1):
            x = x * x % n
            t <<= 1
        if (x != n - 1) and not (t & 1):
            return False
    return True


answer = -1
for p in gen_nums():
    if answer < p and MillerRabinTest(p):
        answer = p
print(answer)