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 <algorithm>
using namespace std;

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

int main(){
    int a,b,n;
    cin >> n;
    int ans = 200 ;

    for ( int a = 1 ; a < n ; a++ ){
        b = n - a;
        int sumab = sum(a) + sum(b);
        ans = min(ans,sumab);
    }
    cout << ans << endl;
}