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 sum_digits(int n) {
    int sum = 0;
    
    while (n > 0) {
        sum += n % 10;
        n  /= 10;
    }

    return sum;
}

int main(void) {
    int n;
    int min = 1e6;

    scanf("%d", &n);
    
    for (int i = 1; i < n; i++) {
        int sum = sum_digits(i) + sum_digits(n - i);
        if (sum < min) min = sum;
    }

    printf("%d\n", min);

    return 0;
}