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;

namespace 練習問題
{
    class Program {
        static void Main(string[] args) {
            debug Debug = new debug();
            string[] input = Console.ReadLine().Split(' ');
            long n = long.Parse(input[0]);
            long k = long.Parse(input[1]);
          	n = n % k;
          	long minval = n;
          	//for(int i=0;i<k;i++){
     
             while(Math.Abs(n - k)< n){            
               n = Math.Abs(n - k);
               
            	if (n < minval){
            		minval = n;
            	}
            }
     
            Console.WriteLine(minval);
        }

        static void bubble_sort(List<List<int>> a) {
            int count=0;
            for (int i = 0; i < a.Count; i++) {
                for (int j = 0; j < a.Count-i-1; j++) {
                    // if (a[j] == a[a.Count - 1]){
                    //     continue;
                    // }
                    count++;
                    if (a[j][1] > a[j+1][1]){
                        int localsave = 0;
                        localsave = a[j+1][1];
                        a[j+1][1] = a[j][1];
                        a[j][1] = localsave;
                        localsave = a[j][0];
                        a[j][0] = a[j+1][0];
                        a[j+1][0] = localsave;
                    }
                }
                //debug(a,"途中" + i);
            }
            // debug(a,"result");
            //Console.WriteLine("回数"+count);
            for (int i = 0; i < a.Count; i++)
            {
                Console.WriteLine(a[i][0]+" "+a[i][1]);
            }
        }
        /* 標準入力と標準出力が使えるかのチェック
        static void echo() {
            string echotest = Console.ReadLine();
            Console.WriteLine(echotest);
        }

        static void HelloWorld(){
            Console.WriteLine("Hello World!");
        }
        */
    }

    public class debug{
        public void Log(string str){
            Console.WriteLine(str);
        }
        public void Log(int str){
            Console.WriteLine(str);
        }
        public void Log(object obj){
            Console.WriteLine(obj);
        }

        public void Log(int[] arr){
            Console.WriteLine(string.Join(",", arr));
        }
        public void Log(string[] arr){
            Console.WriteLine(string.Join(",", arr));
        }
        public void Log(List<int> arr){
            string shuturyoku = "";
            for (int i = 0; i < arr.Count; i++) {
                shuturyoku += arr[i] + " ";
            }
            Console.WriteLine(shuturyoku.TrimEnd(' '));
        }
    }
}