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.Generic;
using System.Linq;
using System.Text;

namespace ConsoleTest
{
    static partial class Program
    {
        static long Calc(long n, long k)
        {
            if (n <= k)
            {
                return Math.Min(n, k - n);
            }
            return Calc(n % k, k);
        }
        static void Main(string[] args)
        {
            var v = Longs();
            long n = v[0];
            long k = v[1];

            Console.WriteLine(Calc(n, k));
        }
    }
    static partial class Program
    {
        public static int Int()
        {
            return int.Parse(Console.ReadLine());
        }
        public static int[] Ints()
        {
            return Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
        }
        public static long[] Longs()
        {
            return Console.ReadLine().Split(' ').Select(s => long.Parse(s)).ToArray();
        }
        public static int[][] MultiInts(int num)
        {
            var result = new int[num][];
            for(int i = 0; i < num; ++i)
            {
                result[i] = Ints();
            }
            return result;
        }
        public static T[] MultiItems<T>(int num, Func<string,T> parser)
        {
            var result = new T[num];
            for(int i =0; i < num; ++i)
            {
                result[i] = parser(Console.ReadLine());
            }
            return result;
        }
    }
}