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;
int n;
int cnt(int x) {
  int ret = 0;
  while (x) {
    ret += x % 10;
    x /= 10;
  }
  return ret;
}
int main() {
  cin >> n;
  int ans = 0x3f3f3f3f;
  for (int i = 1; i <= n / 2; i++) {
    int a = i, b = n - i;
    ans = min(cnt(a) + cnt(b), ans);
  }
  cout << ans << endl;
  return 0;
}