Problem:
Score : 300 points

Problem Statement

Given any integer x, Aoki can do the operation below.

Operation: Replace x with the absolute difference of x and K.

You are given the initial value of an integer N. Find the minimum possible value taken by N after Aoki does the operation zero or more times.

Constraints

0 ≤ N ≤ 10^{18}

1 ≤ K ≤ 10^{18}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the minimum possible value taken by N after Aoki does the operation zero or more times.

Sample Input 1

7 4

Sample Output 1

1

Initially, N=7.

After one operation, N becomes |7-4| = 3.

After two operations, N becomes |3-4| = 1, which is the minimum value taken by N.

Sample Input 2

2 6

Sample Output 2

2

N=2 after zero operations is the minimum.

Sample Input 3

1000000000000000000 1

Sample Output 3

0

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::io;

fn main() {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    let mut iter = buf.split_whitespace();

    let mut n: i64 = iter.next().unwrap().parse().unwrap();
    let k: i64 = iter.next().unwrap().parse().unwrap();

    // 0がでたら終了
    // 暫定Nと同じ値がでたら終了

    // 計算時間短縮の為、n/kの余りを計算
    n = n % k;

    let mut min_n: i64 = n;

    loop {
        let abs: i64 = (n - k).abs();
        if abs == 0 {
            min_n = abs;
            break;
        } else if abs == min_n {
            break;
        } else if abs < n {
            min_n = abs;
        }
        n = abs;
    }

    println!("{}", min_n);
}