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)

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).ok();
    let vec: Vec<&str> = buf.split_whitespace().collect();
    let n: i32 = vec[0].parse().unwrap();

    let mut ans: i32 = n;
    for x in 1..n/2{
        let a = x;
        let b = n-x;
        let c = culdigit(a) + culdigit(b);
        ans = if ans > c {c} else {ans};
    }
    println!("{:?}", ans);
}

fn culdigit(a: i32) -> i32{
    let mut ans = 0;
    let mut cnt = a;
    while cnt > 0{
        ans = ans + (cnt % 10);
        cnt = cnt / 10;
    }
    return ans;
}