import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines

def Miller_Rabin_Primality_Test(N):
    if N==1:
        return False
    NN=N-1
    NN=NN//(NN&-NN)
    if N<4759123141:
        lst=[2,7,61]
    elif N<341550071728321:
        lst=[2,3,5,7,11,13,17]
    else:
        lst=[2,3,5,7,11,13,17,19,23,29,31,37]
    if N in lst:
        return True
    for a in lst:
        n=NN
        p=pow(a,n,N)
        if p==1:
            continue
        while p!=N-1:
            p=p*p%N
            if p==1 or n==N-1:
                return False
            n<<=1
    return True

N=int(readline())
A=list(readline().split())
ans=-1
for tpl in itertools.permutations([i for i in range(N)]):
    P=""
    for i in tpl:
        P+=A[i]
    P=int(P)
    if Miller_Rabin_Primality_Test(P):
        ans=max(ans,P)
print(ans)