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::{stdin, Read};

fn main() {
    let mut input = String::new();
    stdin().read_to_string(&mut input).unwrap();
    let rows: Vec<&str> = input.split('\n').collect();
    let row1_list: Vec<&str> = rows[0].split(' ').collect();
    let n: i64 = row1_list[0].parse().unwrap();
    let k: i64 = row1_list[1].parse().unwrap();
    
    let quotient = n / k;
    
    let mut min: i64 = n - (k * quotient);
    loop {
        let diff = (min - k).abs();
        if diff < min {
            min = diff;
        } else {
            break;
        }
    }
    println!("{}", min);
}