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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <cstdio>
#include <bits/stdc++.h>


using namespace std;

int num(int x){
  int ret = 0;
  while (x > 0){
    ret += x%10;
    x /= 10;
  }
  return ret;
}
int main(){
  int a, b, N, i, j, k, min=1000, sa, sb;
  cin >> N;
  for (a = 1; a < N; a++){
    b = N - a;
    sa = num(a);
    sb = num(b);
    if (sa + sb < min){
      min = sa + sb;
    }
  }
  cout << min << endl;
  return 0;
}