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: Wrong Answer)

#include <iostream>
#include <math.h>
using namespace std;

int ketasum(int x){
    int s=x,t,u=0;
    while(s>0){
        t=s%10;
        u+=t;
        s/=10;
    }
    return u;
}

int main(){
    int n;
    cin >> n;
    int res=100;
    for(int i=2;i<=n-2;i++){
        if(res>ketasum(i)+ketasum(n-i))res=ketasum(i)+ketasum(n-i);
    }
    cout << res << endl;
}