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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.IO;

class Program{
    static void Main(string[] args){
        var arr = Array.ConvertAll(Console.ReadLine().Split(), long.Parse);
        long N = arr[0], K = arr[1];
        var answer = N;
        var isZero = K == 1 || N % 2 == 0 && K == 2;
        if (isZero) answer = 0;
        if (!(N <= Math.Abs(N - K)) && !isZero){
            var mod = N % K;
            answer = mod < Math.Abs(mod - K) ? mod : Math.Abs(mod - K);}
        var writer = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(writer);
        Console.WriteLine(answer);
        Console.Out.Flush();}}