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.IO;
using System.Linq;

class C {
    static StreamWriter Out = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
    static void Main(string[] args) {
        long N, K;
        Input(out N, out K);
        long min1 = N % K;
        long min2 = Math.Abs(min1 - K);
        Print(Math.Min(min1, min2));
        Out.Flush();
    }
    static T ChangeT<T>(string s) => (T)Convert.ChangeType(s, typeof(T));
    static void Input<A>(out A a) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
    }
    static void Input<A, B>(out A a, out B b) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
    }
    static void Input<A, B, C>(out A a, out B b, out C c) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
    }
    static void Input<A, B, C, D>(out A a, out B b, out C c, out D d) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
        d = ChangeT<D>(words[3]);
    }
    static void Input<A, B, C, D, E>(out A a, out B b, out C c, out D d, out E e) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
        d = ChangeT<D>(words[3]);
        e = ChangeT<E>(words[4]);
    }
    static void Input<A, B, C, D, E, F>(out A a, out B b, out C c, out D d, out E e, out F f) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
        d = ChangeT<D>(words[3]);
        e = ChangeT<E>(words[4]);
        f = ChangeT<F>(words[5]);
    }
    static void Inputs<T>(out T[] array) {
        array = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries).Select(s => ChangeT<T>(s)).ToArray();
    }
    static void Print<T>(T s) => Out.WriteLine(s);
    static void Print<T>(params T[] s) => Out.WriteLine(string.Join(" ", s));
    static void Print<T>(IEnumerable<T> e) => Out.WriteLine(string.Join(" ", e));
}