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 (1.14.1) (judge verdict: Wrong Answer)

package main

import (
	"fmt"
	"math"
)

// go run ./main.go < in

func main() {
	var n, k int
	fmt.Scan(&n, &k)

	a, b := n, 0
	for i := 1; ; i++ {
		b = a
		a = n - k*i
		if a < 0 {
			break
		}
	}

	aa := math.Abs(float64(a))
	bb := math.Abs(float64(b))

	// 絶対値
	if aa >= bb {
		fmt.Println(bb)
	} else {
		fmt.Println(aa)
	}
}