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: Wrong Answer)

fn main() {
    let (n, k) = input();
    println!("{}", solve(n, k));
}

fn input() -> (u64, u64) {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).unwrap();
    buf.pop();
    let mut iter = buf.split_whitespace();
    let n: u64 = iter.next().unwrap().parse().unwrap();
    let k: u64 = iter.next().unwrap().parse().unwrap();
    (n, k)
}

fn solve(n: u64, k: u64) -> u64 {
    if n < k { return n; }
    if n % k == 0 { return 0; }
    let a = n % k;
    std::cmp::min(a, k-a)
}