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.Numerics;
using System.Text.RegularExpressions;
namespace AtCoder_Core
{
    class Program
    {
        static void Main(string[] args)
        {
            var line1 = Console.ReadLine().Trim().Split(' ').Select(b => decimal.Parse(b)).ToArray();

            decimal N = line1[0];
            decimal K = line1[1];
            decimal ans = 0;
            decimal min = N;
            if (N % K == 0)
            {
                ans = 0;
            }

            else
            {
                N = N % K;
                while (true)
                {
                    if (Math.Abs(N - K) >= min)
                    {
                        ans = N;
                        break;
                    }

                    N = Math.Abs(N - K);
                    if (min > N)
                    {
                        min = N;
                    }

                }
            }

            Console.WriteLine(ans);
        }
    }
}