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 Rust (1.15.1) (judge verdict: Accepted)

use std::io;
use std::cmp;

fn read_line() -> String {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).ok();
    buf
}


fn main() {
    let n:usize = read_line().trim().parse().unwrap();

    let mut ans = 100000000;

    for i in 1..n/2+1 {
        let mut tmp = 0;
        let mut a = i;
        let mut b = n - i;
        while a > 0 {
            tmp += a % 10;
            a /= 10;
        }
        while b > 0 {
            tmp += b % 10;
            b /= 10;
        }
        ans = cmp::min(ans, tmp);
    }

    println!("{}", ans);

}