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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"fmt"
	"math"
)

func main() {
	// N 商品数
	// M 選択数
	// Ai その商品の票数
	var N, K int
	fmt.Scan(&N, &K)
	if N < K {
		fmt.Println(N)
	} else if N == K || N%K == 0 {
		fmt.Println(0)
	} else {
		x := N
		for {
			r := x - K
			if r < 0 {
				fmt.Println(int(math.Abs(float64(r))))
				break
			} else if r == 0 {
				fmt.Println(0)
			} else {
				x = r
			}
		}
	}

}