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

namespace CSharpSample01
{

	class Program
	{
		static void Main(string[] args)
		{
			var inputNum = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
			var N = inputNum[0];
			var K = inputNum[1];

			var answer = Gcd(N,K);

			if(answer == K)
			{
				Console.WriteLine(0);
			}
			else
			{
				Console.WriteLine(answer);
			}
		}

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