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 PHP7 (7.0.15) (judge verdict: Time Limit Exceeded)

<?php

    // AtCoder Beginner Contest 161
    // C - Replacing Integer

    list($n, $k) = in_ints();

    if ($k == 1) {
        out(0);
    } else if ($k == 2) {
        if ($n % 2 == 0) {
            out(0);
        } else {
            out(1);
        }
    } else {
        out(repint($n, $k));
    }

    function repint($x, $k) {
        $wk = abs($x - $k);
        if ($x <= $wk) {
            return $x;
        }
        return repint($wk, $k);
    }


    /**
    * お手伝い関数さんたち
    */
    function in() {
        return trim(fgets(STDIN));
    }
    function in_int() {
        return (int)in();
    }
    function in_vals() {
        return explode(' ', in());
    }
    function in_ints() {
        return array_map('intval', in_vals());
    }
    function out($s) {
        echo $s . PHP_EOL;
    }
    function yes() {
        out('Yes');
    }
    function no() {
        out('No');
    }