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) {
             
    //echo floor($n / $k) . PHP_EOL;
    //echo (int)$n . PHP_EOL;
    //echo (int)$k . PHP_EOL;
    //echo (int)(floor($n / $k)) * ((int)$k);
        $n = (int)$n - ((int)(floor($n / $k)) * (int)$k); 
    }        
    //echo $n . PHP_EOL;
 
    while (true) {
        # code...
        //echo 'n1 = ' . $n . PHP_EOL;
        //echo 'k1 = ' . $k . PHP_EOL;

        $a = abs((int)$n - (int)$k);
        
        //echo 'a = ' . $a . PHP_EOL;
 
        if ((int)$n > (int)$a){
            $n = $a;
        } else {
            break;
        }
        
        //echo 'n = ' . $n . PHP_EOL;
    }
    echo $n;
?>