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 ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
          string[] Input = Console.ReadLine().Split(' ');
          long N = long.Parse(Input[0]);
          long K = long.Parse(Input[1]);
          long abs = 1000000000000000000;
          bool flag = false;
          do
          {
            if(K == 1 || N == K)
            {
              flag = true;
              abs = 0;
            }
            else if((N / K > K) && (N % K == 0))
            {
              N /= K;
            }
            else if(abs > Math.Abs(N - K))
            {
          	abs = Math.Abs(N - K);
            N = Math.Abs(N - K);
            }
            else
            {
             flag = true; 
            }
          }while(!flag);
          Console.WriteLine(abs);
          
        }
    }
}