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: Time Limit Exceeded)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace AtCoder2020Ned
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            long n = long.Parse(input[0]);
            long k = long.Parse(input[1]);

            long Answer =Sub(n,k);
            
            Console.Write(Answer);
            Console.Read();
        }
         public static long Sub(long n,long k)
        {
            for (;;)
            {
                if (k == 1)
                {
                    return 0;
                }
                else if (n < Math.Abs(n - k))
                {
                    return n;                    
                }
                n = Math.Abs(n - k);
            }
        }
    }
}