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>
#include <stdlib.h>

int sum_digit(int x) {
  int s = 0;

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

int main( int argc, char *argv[] ) {
  int i, n;
  scanf("%d", &n);
  int min = n;
  //printf("%d %d\n", n, sum_digit(n));

  for (i=1; i<=n/2; i++) {
    int ss = sum_digit(i) + sum_digit(n-i);
    if (min > ss) min = ss;
  }
  printf("%d\n", min);
  return 0;
}