Problem:
Score : 300 points

Problem Statement

Takahashi, who lives on the number line, is now at coordinate X. He will make exactly K moves of distance D in the positive or negative direction.

More specifically, in one move, he can go from coordinate x to x + D or x - D.

He wants to make K moves so that the absolute value of the coordinate of the destination will be the smallest possible.

Find the minimum possible absolute value of the coordinate of the destination.

Constraints

-10^{15} \leq X \leq 10^{15}

1 \leq K \leq 10^{15}

1 \leq D \leq 10^{15}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X K D

Output

Print the minimum possible absolute value of the coordinate of the destination.

Sample Input 1

6 2 4

Sample Output 1

2

Takahashi is now at coordinate 6. It is optimal to make the following moves:

Move from coordinate 6 to (6 - 4 =) 2.

Move from coordinate 2 to (2 - 4 =) -2.

Here, the absolute value of the coordinate of the destination is 2, and we cannot make it smaller.

Sample Input 2

7 4 3

Sample Output 2

1

Takahashi is now at coordinate 7. It is optimal to make, for example, the following moves:

Move from coordinate 7 to 4.

Move from coordinate 4 to 7.

Move from coordinate 7 to 4.

Move from coordinate 4 to 1.

Here, the absolute value of the coordinate of the destination is 1, and we cannot make it smaller.

Sample Input 3

10 1 2

Sample Output 3

8

Sample Input 4

1000000000000000 1000000000000000 1000000000000000

Sample Output 4

1000000000000000

The answer can be enormous.

Solution in Rust (1.42.0) (judge verdict: Wrong Answer)

use std::io::*;
//use std::str::*;

macro_rules! get_in {
	() => {
		{
			let mut buf = String::new();
			stdin().read_line(&mut buf).ok();
			
			buf.replace("\n", "")
		}
	}
}

fn main() {
	let t = get_in!()
				.split_whitespace()
				.map(|v| v.parse::<i64>().unwrap())
				.collect::<Vec<i64>>();

	let mut super_uhouho_land = false;
	let mut hage = 0_i64;
	let mut last = 0_i64;
	let (mut x, k, d) = ( t[0], t[1], t[2] );

	for v in 0..k {
		if x > 0 {
			x-=d;
		} else {
			x+=d;
		}
		last = x;
		hage = last;
	}

	println!("{}", x);
}