using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using static System.Console;
using static System.Math;
using static Atcoder.IO;

namespace Atcoder
{
    class Program
    {
        static StreamWriter sw = new StreamWriter(OpenStandardOutput()) { AutoFlush = false };
        static void Main(string[] args)
        {
            try
            {
                SetOut(sw);
                Solve.Answer();
                Out.Flush();
            }
            catch (Exception ex)
            {
                WriteLine(ex.ToString());
                Out.Flush();
            }
        }
    }

    public class Solve
    {
        public static void Answer()
        {
            var xkd = RSLong;
            var x = xkd[0];
            var k = xkd[1];
            var d = xkd[2];

            if (x > 0)
            {
                if (x / d > k)
                {
                    WriteLine(x - d * k);
                    return;
                }
                var k2 = k - x / d;
                if (k2 % 2 == 0)
                {
                    WriteLine(x % d);
                    return;
                }
                else
                {
                    WriteLine(d - x % d);
                    return;
                }
            }
            else if (x < 0)
            {
                x *= -1;
                if (x / d > k)
                {
                    WriteLine(x - d * k);
                    return;
                }
                var k2 = k - x / d;
                if (k2 % 2 == 0)
                {
                    WriteLine(x % d);
                    return;
                }
                else
                {
                    WriteLine(d - x % d);
                    return;
                }
            }
            else
            {
                if (k % 2 == 0)
                {
                    WriteLine(0);
                    return;
                }
                else
                {
                    WriteLine(d);
                }
            }
        }
    }

    public class IO
    {
        #region Input
        public static int RInt => int.Parse(ReadLine());
        public static long RLong => long.Parse(ReadLine());
        public static double RDouble => double.Parse(ReadLine());

        public static string[] RSString => ReadLine().Split();
        public static int[] RSInt => ReadLine().Split().Select(s => int.Parse(s)).ToArray();
        public static long[] RSLong => ReadLine().Split().Select(s => long.Parse(s)).ToArray();
        public static double[] RSDouble => ReadLine().Split().Select(s => double.Parse(s)).ToArray();
        #endregion

        #region Output
        public static void OutJoinSpace<T>(IEnumerable<T> list) => WriteLine(string.Join(" ", list));
        public static void WriteLineYes_or_No(bool flag) => WriteLine(flag ? "Yes" : "No");
        public static void WriteLineYES_or_NO(bool flag) => WriteLine(flag ? "YES" : "NO");
        #endregion
    }

    public class Mod
    {
        #region
        private readonly static long M = 1000000007;

        public static long Add(long a, long b) => (a * b) % M;
        public static long Sub(long a, long b) => (a - b) % M >= 0 ? (a - b) % M : (a - b) % M + M;
        public static long Multi(long a, long b) => (a * b) % M;
        #endregion
    }
}

Measured memory_bytes: 28240