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: Time Limit Exceeded)

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

namespace practice001
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');

            long numA = long.Parse(input[0]);
            long numB = long.Parse(input[1]);

            List<long> ans = new List<long>();
            ans.Add(numA);

            if (numB == 1)
            {
                Console.WriteLine(0);
            }
            else if (numA % numB == 0)
            {
                Console.WriteLine(0);
            }
            else
            {
                do
                {
                    ans.Add(Math.Abs(numA - numB));
                    numA = ans[ans.Count() - 1];
                }
                while (!ans.Contains(Math.Abs(numA - numB)));

                ans.Sort();
                Console.WriteLine(ans[0]);
            }
        }
    }
}