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 Scala (2.13.1) (judge verdict: Accepted)

//object D {
object Main {
  import InOut._
  def main(args: Array[String]): Unit = {

    var x, k, d = nextLong
    x = Math.abs(x)
    val steps = Math.min(k, x / d)
    x -= steps * d
    k -= steps
    x -= (k % 2) * d

    out.println(Math.abs(x))

    out.flush()
  }
 
  final object InOut {
    val in = new java.io.BufferedReader(new java.io.InputStreamReader(System.in))
    val out = new java.io.PrintWriter(System.out, false)
    private[this] var tokenizer: java.util.StringTokenizer = _
    def nextToken: String = {
      while (tokenizer == null || !tokenizer.hasMoreTokens)
        tokenizer = new java.util.StringTokenizer(in.readLine)
      tokenizer.nextToken
    }
    def nextInt = Integer.parseInt(nextToken)
    def nextLong = java.lang.Long.parseLong(nextToken)
    def nextBig = BigInt(nextToken)
    def nextInts(n: Int) = Array.fill(n) { nextInt }
    def nextLongs(n: Int) = Array.fill(n) { nextLong }
    def nextBigs(n: Int) = Array.fill(n) { nextBig }
    def nextLine = in.readLine
  }
}