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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
static class Program
{
	static int[] ReadInts(this TextReader reader) => reader.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
	static long[] ReadLongs(this TextReader reader) => reader.ReadLine().Split(' ').Select(s => long.Parse(s)).ToArray();
	static IEnumerable<int[]> ReadInts(this TextReader reader, int count)
	{
		for (long i = 0; i < count; ++i)
			yield return reader.ReadInts();
	}

	static IEnumerable<long[]> ReadLongs(this TextReader reader, long count)
	{
		for (long i = 0; i < count; ++i)
			yield return reader.ReadLine().Split(' ').Select(s => long.Parse(s)).ToArray();
	}
	
	public static void Main(string[] args)
	{
		var input = Console.In.ReadLongs();
		var n = input[0]; var k = input[1];
		var n2 = n;
		do {
			n = n2 % k;
			n2 = Math.Abs(n - k);
		} while(n2 < n);
		Console.WriteLine(n);
	}
}