import java.security.KeyStore.TrustedCertificateEntry
import java.util
import java.util.regex.Pattern
import java.util.{ArrayList, Collections, Comparator, List => JList}

import scala.collection.immutable.TreeMap
import scala.math._
import scala.collection.mutable
import scala.collection.mutable.{ArrayBuffer, ListBuffer}
import scala.util.{Failure, Success, Try}

object Main{
  val LS = "\n"
  def main(args: Array[String]): Unit = {
    if (sys.env.getOrElse("TEST", "")=="1"){
      println(test());
    }else{
      val input=io.Source.stdin.getLines().mkString(LS);
      println(solve(input).trim());
    }
  }

  def init (nRows: Int, nCols: Int, default: Int): Array[Array[Int]] = Array.tabulate(nRows,nCols)((x, y) =>  default)

  def sortIgnoreCase1(list: JList[String]): JList[String] = {
    val r = new ArrayList[String](list)
    Collections.sort(r, new Comparator[String] {
      override def compare(o1: String, o2: String): Int = o1.compareToIgnoreCase(o2)
    })
    r
  }

  def solve(input: String): String = {
    val Array(x, k, d) = input.split(" ").map(_.toLong)
    if (k <= x.abs / d) return (x.abs - k * d).toString
    val reach0 = x / d
    if ((k - reach0 ) % 2 == 0) (x.abs % d).toString else ((x.abs % d) - d).abs.toString
  }

  def divideDigits(num: Long, base: Long = 10L): List[Long] = {
    def proc(num: Long, base: Long, flg: Boolean): List[Long] = {
      var flag = flg
      val quotient = num / base
      val remainder = if (num % base == 0) {
        flag = true
        base
      } else if (flag) {
        flag = false
        val temp = num % base - 1
        if (temp == 0) {
          flag = true
          base - 1
        } else temp
      } else {
        flag = flg
        num % base
      }
      quotient match {
        case 0 =>
          if (flag) {
            List.empty
          } else List(remainder)
        case _ => remainder :: proc(quotient, base, flag)
      }
    }

    proc(num, base, false).reverse//.filterNot(_ == 0)
  }


  def medianCalculator(seq: Seq[Long]): Long = {
    //In order if you are not sure that 'seq' is sorted
    val sortedSeq = seq.sortWith(_ < _)

    if (seq.size % 2 == 1) sortedSeq(sortedSeq.size / 2)
    else {
      val (up, down) = sortedSeq.splitAt(seq.size / 2)
      (up.last + down.head) / 2
    }
  }

  def factorize(x: Long): List[Long] = {
    def foo(x: Long, a: Long = 2, list: List[Long] = Nil): List[Long] = a*a > x match {
      case false if x % a == 0 => foo(x / a, a    , a :: list)
      case false               => foo(x    , a + 1, list)
      case true                => x :: list
    }
    foo(x)
  }

  def divisors(n: Int): Vector[Int] = {
    val halfList = (1 to sqrt(n).toInt).toVector.filter(n % _ == 0).map(_.toInt)
    val reversedList = if (sqrt(n).floor == sqrt(n)) halfList.reverse.tail.map(n/_) else halfList.reverse.map(n/_)
    halfList ++ reversedList
  }

  def gcd(m: Long, n: Long): Long = n match {
    case 0 => m
    case _ => gcd(n, m % n)
  }
  def lcm(a: Long, b: Long): Long = a * b / gcd(a, b)

  val tests=List(
    """6 2 4""".stripMargin -> """2
                                 |""".stripMargin,
    """7 4 3""".stripMargin -> "1",
    """10 1 2""".stripMargin -> "8",
    """1000000000000000 1000000000000000 1000000000000000""".stripMargin -> "1000000000000000"
  )

  def test():String= {
    return tests.map{case (i,o)=>(i.trim(),o.trim())}
      .zipWithIndex.map{
      case ((input,outputExpect),i)=>{
        val output=solve(input).trim();
        s"test${i+1}:"+(if(output==outputExpect){
          "Passed"
        }else{
          s"Failed\nexpect:\n${outputExpect}\noutput:\n${output}"
        })
      }}
      .mkString("\n");
  }
}


Measured memory_bytes: 55372