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: Time Limit Exceeded)

using System;
namespace kozaiyApp
{
    public class C
    {
        static ulong ans;
        static void Main()
        {
            string[] input = Console.ReadLine().Split(' ');
            ulong N = ulong.Parse(input[0]);
            ulong K = ulong.Parse(input[1]);

            ans = N;
            Recursion(N, K);
            Console.WriteLine(ans);
        }

        static void Recursion(ulong n, ulong k)
        {
            ulong x = n > k ? n - k : k - n;
            if (x < n)
            {
                ans = x;
                Recursion(x, k);
            }
        }
    }
}