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)

fn read<T: std::str::FromStr>() -> T {
   let mut s = String::new();
   std::io::stdin().read_line(&mut s).ok();
   s.trim().parse().ok().unwrap()
}

fn readn<T: std::str::FromStr>(delimiter: &str) -> Vec<T> {
   let s = read::<String>();
   s.split(delimiter)
      .map(|e| e.parse().ok().unwrap())
      .collect::<Vec<T>>()
}

fn main() {
   let nk = readn::<i64>(" ");
   let n = nk[0];
   let k = nk[1];
   let l = n / k;
   let ans = std::cmp::min((n - k * l).abs(), (n - k * (l + 1)).abs());
   println!("{}", ans);
}