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;

class Program
{
    static void Main(string[] args)
    {
        var line1 = Console.ReadLine()
            .Split(' ')
            .Select(n => long.Parse(n))
            .ToList();
        var N = line1[0];
        var K = line1[1];

        var minN = N;

        if (N > K)
        {
            var x = (N / K) * K;
            N -= x;
        }
        for (int i = 0; i < 100; i++)
        {
            if (N > K)
            {
                // Console.WriteLine($"{i:0000} : N={N} K={K}");
                N = N - K;
            }
            else
            {
                N = K - N;
            }

            if (N < minN)
            {
                minN = N;
                if (minN == 0) break;
            }
            // Console.WriteLine($" => N={N}");
        }

        Console.WriteLine(minN);
    }
}