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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

class Progaram
{
    static void Main(string[] args)
    {
        var l = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
        long n = l[0]; long k = l[1];
        long ans;
        if (k == 1) ans = 0;
        else if (n < k) ans = new long[] { n, k - n }.Min();
        else if (n % k == 0) ans = 0;
        else ans = Gcd(n, k);
        Console.WriteLine(ans);
    }

    static long Gcd(long a, long b)
    {
        if (a < b)
            return Gcd(b, a);
        while (b != 0)
        {
            long remainder = a % b;
            a = b;
            b = remainder;
        }
        return a;
    }
}