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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;

namespace test
{
    class MainClass
    {
        public static void Main(string[] args)
        {

            //問題155
            //Console.WriteLine("test");


            string[] line = Console.ReadLine().Split(' ');

            long x = long.Parse(line[0]);
            long k = long.Parse(line[1]);
            long d = long.Parse(line[2]);

            long ans = 0;

            if (x > 0)
            {
                if (x - k * d > 0)
                {
                    ans = x - k * d;
                }

                else if (x % d == 0)
                {
                    long count = x / d;

                    k = k - count;

                    if (k % 2 == 0)
                        ans = 0;
                    else
                        ans = d;
                }

                else
                {
                    x %= d;

                    long count = x / d;
                    k = k - count;

                    if (k % 2 == 0)
                        ans = x;
                    else
                        ans = d - x;

                    //ans = Math.Min(x, d - x);
                }

            }

            else if (x < 0)
            {
                if (x + k * d < 0)
                {
                    ans = x + k * d;
                    ans = -ans;
                }

                else if ((-x) % d == 0)
                {
                    long count = (-x) / d;

                    k = k - count;

                    if (k % 2 == 0)
                        ans = 0;
                    else
                        ans = d;
                }

                else
                {
                    x = -x;
                    x %= d;

                    //x = -x;

                    //ans = Math.Min(-x, d + x);

                    long count = x / d;
                    k = k - count;

                    if (k % 2 == 0)
                        ans = x;
                    else
                        ans = d - x;
                }
            }

            else
            {
                if (k % 2 == 0)
                {
                    ans = 0;
                }
                else
                {
                    ans = d;
                }
            }



            Console.WriteLine(ans);

        }


    }





    
}