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

namespace competitive_programming
{
    class Program
    {
        static void Main(string[] args)
        {
            var main = new Program();
            main.solve();
        }

        void solve()
        {
            long[] nk = Console.ReadLine().Split(' ').Select(val => long.Parse(val)).ToArray();
            long n = nk[0];
            long k = nk[1];
            n = n % k;
            while(Math.Abs(n - k) <= n)
            {
                n = Math.Abs(n - k);
            }
            Console.WriteLine(n);
        }
    }

    struct Vector2
    {
        public Vector2(long x, long y)
        {
            this.x = x;
            this.y = y;
        }
        public long x;
        public long y;
    }

    struct Vector3
    {
        public int x;
        public int y;
        public int z;
    }
}