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;

namespace abc161c
{
    class Program
    {
        static void Main(string[] args)
        {
            //==========================================================================================================================
            //1) input
            List<decimal> input = Console.ReadLine().Split(' ').Select(decimal.Parse).ToList();
            decimal n = input[0];
            decimal k = input[1];

            decimal tmp = Math.Truncate(n / k);
            decimal start = n - tmp * k;


            decimal n_before = start + 1;
            while (start < n_before)
            {
                n_before = start;
                start = Math.Abs(start - k);
            }




            //==========================================================================================================================
            //2) output
            Console.WriteLine(n_before);
        }
    }
}