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 digits_sum(int n){
    int sum = 0;
    div_t tmp;
    while(n != 0){
         tmp = div(n, 10);
         sum += tmp.rem;
         n = tmp.quot;
    }
    return sum;
}

int main(void){
    int i, N;
    scanf("%d", &N);
    int min = 100, tmp;
    for(i = 1; i <= N/2; i++){
        tmp = digits_sum(i) + digits_sum(N-i);
        if(tmp < min) min = tmp;
    }
    printf("%d", min);
    return 0;
}