Problem:
Score : 200 points

Problem Statement

Takahashi has two positive integers A and B.

It is known that A plus B equals N.
Find the minimum possible value of "the sum of the digits of A" plus "the sum of the digits of B" (in base 10).

Constraints

2 ≤ N ≤ 10^5

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the minimum possible value of "the sum of the digits of A" plus "the sum of the digits of B".

Sample Input 1

15

Sample Output 1

6

When A=2 and B=13, the sums of their digits are 2 and 4, which minimizes the value in question.

Sample Input 2

100000

Sample Output 2

10

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int digit_sum(int x){
  int s=0;
  while(x>0){
      s+=x%10;
      x=x/10;
  }
  return s;
}

int main(void){
  int i,n,m,min=100,s=0;
  scanf("%d",&n);
  m=n/2;
  for(i=1;i<=m;i++){
    s=digit_sum(i)+digit_sum(n-i);
    if(s<min){
      min=s;
    }
    s=0;
  }
  printf("%d\n",min);
  return 0;
}