import strutils
import sequtils
import algorithm
import bitops

const Mod : int = 1_000_000_007

proc powMod*(n : int, x : int, m = Mod) : int =
  if x == 0: return 1
  if n == 1: return 1
  if x == 1: return (n mod m)
  if x mod 2 == 0:
    return powMod((n * n) mod m, x div 2, m) mod m
  else:
    return n * powMod((n * n) mod m, x div 2, m) mod m

proc millerRabin*(n : int) : bool =
  if n <= 1: return false
  if n == 2 and n == 3 and n == 5: return true
  if n mod 2 == 0: return false
  let
    s = popcount(n-1)
    d = (n - 1) div (1 shl s)
  var xs = @[2, 7, 61, 103]
  if n >= 4_759_123_141 and n < 341_550_071_728_321:
    xs = @[2,3,5,7,11,13,17]
  if n in xs : return true
  for a in xs :
    if powMod(a,d,n) == 1: continue
    let notPrime = toSeq(0..<s).allIt(powMod(a,d*(1 shl it),n) != n-1)
    if notPrime: return false
  return true

proc conc(A : seq[int]) : int =
  for a in A:
    if a < 10: result = 10 * result + a
    else:result = 100 * result + a

var
  _ = stdin.readLine
  A = stdin.readLine.split.map(parseInt)
  ans = -1
A.sort()

while true:
  let p = A.conc()
  if ans < p and p.millerRabin(): ans = p
  if not nextPermutation(A): break
echo ans