Python :

import math
def suShu(n):
   f=  True
   for i in range(2,int(math.sqrt(n)) + 1 ):
      if n % i == 0:
         f = False
         break
   return f and n != 1

def chaiwei(n):
    min = 0  # min 存放2段之和最小的素数
    f = True  # 表示是否为第一次获取素数 
    for i in range(1,len(n)):
       x = int(n[0:i]) + int(n[i:])
       if suShu(x) :
          if f:
             min = x;
             f = False
          else:
             if x < min:
                min = x;
    return min

n = input();
r = chaiwei(n)
if r == 0:
    print(-1)
else:
    print(r)