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: Wrong Answer)

using System;
//using System.Collections.Generic;
public class ProCon
{
    public static void Main(){     
        string[] line1 =　Console.ReadLine().Split(' ');

        long N = long.Parse(line1[0]);
        long K = long.Parse(line1[1]);

        long ret = N + 1;
        if(K == 1)
        {
            Console.WriteLine(0);
        }
        /*
        else if(N == 1)
        {
            Console.WriteLine(1);
        }
        */
        else
        {
            if(N> K)
            {
                N = N % K;
            }
            while(ret > 0)
            {
                ret = myMethod(N, K);
                if(ret > N) break;
                N = ret;
            }
            Console.WriteLine(N);
        }
    }
    public static long myMethod(long x, long y)
    {
        long ret = 0;
        if(x < y)
        {
            ret = y - x;
        }
        if(y < x)
        {
            ret = x - y;
        }
        if(x == y)
        {
            ret = -1;
        }
        return ret;
    }
}