class Integer
    def prime?
      n = self.abs()
      return true if n == 2
      return false if n == 1 || n & 1 == 0
      d = n-1
      d >>= 1 while d & 1 == 0
      5.times do                               # 20 は上の説明の k に相当
        a = rand(n-2) + 1
        t = d
        y = ModMath.pow(a,t,n)                  # 実装コードは下にある
        while t != n-1 && y != 1 && y != n-1
          y = (y * y) % n
          t <<= 1
        end
        return false if y != n-1 && t & 1 == 0
      end
      return true
    end
  end
  
  module ModMath
    def ModMath.pow(base, power, mod)
      result = 1
      while power > 0
        result = (result * base) % mod if power & 1 == 1
        base = (base * base) % mod
        power >>= 1;
      end
      result
    end
  end

n = gets.to_i
arr = gets.chomp.split

ans = -1
arr.permutation(n) do |a|
    x = a.join.to_i
    if x.prime?
        ans = (x > ans ? x : ans)
    end
end
p ans