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: Accepted)

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using System.Numerics;

namespace abc161
{
    class Program
    {
        static void Main(string[] args)
        {
            if (File.Exists("input.txt"))
            {
                Console.SetIn(new StreamReader("input.txt"));
            }
			solve_abc161C();
        }
        public static void solve_abc161C()
        {
            long[] nk = Array.ConvertAll(Console.ReadLine().Split(), long.Parse);
            long n = nk[0];
            long k = nk[1];
            long r = n % k;
            if (n < k)
            {
                Console.WriteLine(Math.Min(n , Math.Abs(n - k)));
            }
            else if (r == 0)
            {
                Console.WriteLine(0);
            }
            else
            {
                Console.WriteLine(Math.Abs(r - k));
            }
        }

        public static void solve_abc161B()
        {
            int[] nm = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            int n = nm[0];
            int m = nm[1];
            int[] a = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            int sum = 0;
            for (int i = 0; i < n; i++)
            {
                sum += a[i];
            }
            int cnt = 0;
            for (int i = 0; i < n; i++)
            {
                if (a[i] >= (double)sum / (4 * m))
                {
                    cnt++;
                }
            }
            Console.WriteLine(cnt >= m ? "Yes" : "No");
        }

        public static void solve_abc161A()
        {
            int[] xyz = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            Console.WriteLine("{0} {1} {2}", xyz[2], xyz[0],xyz[1]);
        }
    }
}