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<bits/stdc++.h>
using namespace std;

long sumdig(long A)
{
    long sum=0,rem;

    while(A>0)
    {
        rem=A%10;
        A=A/10;
        sum+=rem;
    }

    return sum;
}

int main()
{
    long N,A,B,ans=INT_MAX;
    cin>>N;
    A=1;
    B=N-A;

    while(B>= N/2)
    {
      ans= min(ans,sumdig(A) + sumdig(B));

      A=A+1;
      B=B-1;
    }

    cout<<ans;
}