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::collections::{HashMap, VecDeque};
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")
}

//struct Main {
//    x: i32,
//    y: i32,
//    z: i32,
//}
//impl Main {
//    fn invoke(&mut self) {
//        println!("{} {} {}", self.z, self.x, self.y);
//    }
//}

fn main() {
//    Main { x: x, y: y, z: z }.invoke()

    let n: i64 = read();
    let k: i64 = read();

    let rem = n % k;
    if rem == 0 {
        println!("{}", 0);
    } else {
        let reversed_rem = k - rem;
        if rem < reversed_rem {
            println!("{}", rem);
        } else {
            println!("{}", reversed_rem);
        }
    }
}