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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace abc161_c
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] NK = Console.ReadLine().Split(' ');
            long N = long.Parse(NK[0]);
            long K = long.Parse(NK[1]);

            if (N % K == 0)
            {
                Console.WriteLine(0);
            }
            else
            {
                N = N % K;

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

                Console.WriteLine(N);
            }

            Console.Read();
        }
    }
}