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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner fs = new Scanner(System.in);
        long x = fs.nextLong();
        long k = fs.nextLong();
        long d = fs.nextLong();

        long moves = x/d ;
        moves = Math.min(k,moves);
        long rem = k - moves;

        long pos_g = -1 ;
        long neg_g = Long.MAX_VALUE ;

        pos_g = x - moves * d;
        if(rem%2==1){
            pos_g += d ;
        }
        if(rem>0){
            neg_g = x - (moves+1) * d ;
            rem--;
            if(rem%2==1){
                neg_g += d ;
            }
        }

        if(neg_g!=Long.MAX_VALUE) {
            System.out.println(Math.abs(Math.min(pos_g, neg_g)));
        }else{
            System.out.println(Math.abs(pos_g));
        }









    }
}