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: Wrong Answer)

#include <stdio.h>
#include <math.h>
int main(void){
 int A, B, N, i, j, x, y, a, b, c, a1, a2;
 scanf("%d", &N);
 for(i=1; i<N; i++){
   A=N-i;
   a1=N-i;
   B=i;
   a2=i;
   for(j=1; A>0; j++){
    A/=10;
   }
   x=j;
   for(j=x; j>=0; j--){
     a+=a1/pow(10,j);
     a1-=a1/pow(10,j);
   }
   for(j=1; B>0; j++){
    B/=10;
   }
   y=j;
   for(j=y; j>=0; j--){
     b+=a2/pow(10,j);
     a2-=a2/pow(10,j);
   }
   if(c<a+b){
     c=a+b;
   }
   a=0;
   b=0;
 }
 printf("%d\n", c);
}