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 PHP (5.6.30) (judge verdict: Wrong Answer)

<?php
    $s = explode(' ', trim(fgets(STDIN)));
    $n = (int)$s[0];
    $k = (int)$s[1];

    // 最初にひけるだけひく

    if ((int)$n > (int)$k) {
        $n = $n - (floor($n / $k) * $k); 
    }        

    while (true) {
        # code...
        $a = abs((int)$n - (int)$k);

        if ((int)$n > (int)$a){
            $n = $a;
        } else {
            break;
        }
    }
    echo $n;
?>