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 (1.42.0) (judge verdict: Wrong Answer)

use std::io::*;
use std::str::FromStr;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

fn switch_number(n1: &mut i32, n2: &mut i32) {
    let tmp = *n1;
    *n1 = *n2;
    *n2 = tmp;
}

fn main() {
    let mut n: i128 = read();
    let mut k: i128 = read();

    // let mut min: i128 = 10000000000000000000;

    if n == 1 || k == 1 || n == 0 || k == 0 || n == k || n == 2 * k || 2 * n == k {
        println!("0")
    } else {
        println!("{}", gcd(n, k));
    }
}

fn gcd(a: i128, b: i128) -> i128 {
    if b == 0 {
        a
    } else {
        gcd(b, a % b)
    }
}