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.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Collections.Generic;

class Program
{
	static long K;

	//|x - K|を計算
	static long Diff(long x){
			long diff = 0;
			if(x >= K){
					diff = x - K;
			}else{
					diff = K - x;
			}

			return diff;
	}

	//Main
	static void Main(string[] args)
	{
		//読み込む
		string[] line = Console.ReadLine().Split(' ');
		long N = long.Parse(line[0]);
		K = long.Parse(line[1]);

		//二個前までの数を格納する配列
		long[] before = new long[2];
		//最小値を格納
		long min = N;

		if(N == K){
				min = 0;
		}
		else if(N < K){
				min = Math.Min(N, (K - N));
		}
		else{
				long rem = N % K;
				min = Math.Min(rem, (K-rem));
		}

		Console.WriteLine(min);

	}
}