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 C# (.NET Core 3.1.201) (judge verdict: Runtime Error)

using System;
class Program {
    static void Main (string[] args) {
        string[] input = Console.ReadLine ().Split (' ');
        int X = int.Parse (input[0]);
        int K = int.Parse (input[1]);
        int D = int.Parse (input[2]);
        while (K > 0) {
            if (Math.Abs (X) < Math.Abs (D)) {
                if ((K % 2) == 0)
                    Console.WriteLine ((int) Math.Abs (X));
                else
                    Console.WriteLine ((int) Math.Abs (X + D) < (int) Math.Abs (X - D) ? (int) Math.Abs (X + D) : (int) Math.Abs (X - D));
            } else if (Math.Abs (X - D) < Math.Abs (X + D))
                X -= D;
            else
                X += D;
            K--;
        }
    }
}