#include <stdio.h>
int main()
{
  int n;
  scanf("%d",&n);
  int maxint=0;
  int minint=9;
  int temp=n;
  while (temp>0)
  {
   int digit=temp%10;
   if (digit>maxint)
   maxint=digit;
   else if (digit<minint)
   minint=digit;
   temp=temp/10;
  }
  int *ptrmaxint=&maxint;
  int *ptrminint=&minint;
  int *ptrsum=ptrmaxint;
  
  *ptrsum+=*ptrminint;
  printf("%d",*ptrsum);
}