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

namespace Contest
{
  class Program
  {
    static void Main(string[] args)
    {
      ABC175.C();
    }
    class ABC175
    {
      public static void A()
      {
        var S = Read.Str();
        if (S == "RRR")
        {
          Console.WriteLine(3);
        }else if (S.Contains("RR"))
        {
          Console.WriteLine(2);
        }else if (S.Contains("R"))
        {
          Console.WriteLine(1);
        }
        else
        {
          Console.WriteLine(0);
        }
      }
      public static void B()
      {
        var N = Read.Int();
        var L = Read.LongN();
        long count = 0;
        for(int i = 0; i < N; ++i)
        {
          for (int j = i + 1; j < N; ++j)
          {
            for(int k = j + 1; k < N; ++k)
            {
              var x = new long[] { L[i], L[j], L[k] }.Distinct().OrderBy(x => x).ToArray();
              if (x.Length < 3) { continue; }
              if (x[0] + x[1] > x[2])
              {
                count++;
              }
            }
          }
        }
        Console.WriteLine(count);
      }
      public static void C()
      {
        var X = Read.Long();
        var K = Read.Long();
        var D = Read.Long();
        var diff = X / D;
        long min = (long)1e18;
        if ((double)K * (double)D < 1e18)
        {
          min = Math.Min(min, Math.Abs(X - D * K));
          min = Math.Min(min, Math.Abs(X + D * K));
        }
        for (long i = (K - diff) / 2 - 100; i < (K - diff) / 2 + 100; ++i)
        {
          var j = K - i;
          if (i < 0 || j < 0) { continue; }
          var Y = X + (i - j) * D;
          min = Math.Min(min, Math.Abs(Y));
        }
        Console.WriteLine(min);
      }
      public static void D()
      {

      }
      public static void E()
      {

      }
      public static void F()
      {

      }
    }

    class Bound
    {
      public static int Lowerbound<T1, T2>(SortedList<T1, T2> list, T1 x) where T1 : IComparable<T1>
      {
        return Lowerbound(list.Keys, x);
      }
      public static int Upperbound<T1, T2>(SortedList<T1, T2> list, T1 x) where T1 : IComparable<T1>
      {
        return Upperbound(list.Keys, x);
      }
      public static int Lowerbound<T>(IList<T> list, T x) where T : IComparable<T>
      {
        int min = 0;
        int max = list.Count;
        while (min < max)
        {
          var mid = (min + max) / 2;
          if (list[mid].CompareTo(x) >= 0)
          {
            max = mid;
          }
          else
          {
            min = mid + 1;
          }
        }
        return max;
      }
      public static int Upperbound<T>(IList<T> list, T x) where T : IComparable<T>
      {
        int min = 0;
        int max = list.Count;
        while (min < max)
        {
          var mid = (min + max) / 2;
          if (list[mid].CompareTo(x) > 0)
          {
            max = mid;
          }
          else
          {
            min = mid + 1;
          }
        }
        return max;
      }

    }


    class Util
    {
      public static T[,] Gen<T>(int r, int c, T v)
      {
        var matrix = new T[r, c];
        for (int i = 0; i < r; ++i)
        {
          for (int j = 0; j < c; ++j)
          {
            matrix[i, j] = v;
          }
        }
        return matrix;
      }
      public static long[] ASum(long[] array)
      {
        var res = new long[array.Length + 1];
        for (int i = 0; i < array.Length; ++i)
        {
          res[i + 1] = res[i] + array[i];
        }
        return res;
      }
      public static long[,] ASum(long[,] matrix)
      {
        var N = matrix.GetLength(0);
        var M = matrix.GetLength(1);
        var res = new long[N + 1, M + 1];
        for(int i = 0; i < N; ++i)
        {
          for(int j = 0; j < M; ++j)
          {
            res[i + 1, j + 1] = res[i, j + 1] + res[i + 1, j] - res[i, j] + matrix[i, j];
          }
        }
        return res;
      }
      public static MyDict<T, long> Frequency2<T>(T[] array)
      {
        var dict = new MyDict<T, long>();
        foreach (var a in array)
        {
          dict[a]++;
        }
        return dict;
      }
      public class MyDict<T1, T2> : Dictionary<T1, T2>
      {
        public new T2 this[T1 key]
        {
          get { if (!base.ContainsKey(key)) { base.Add(key, default(T2)); } return base[key]; }
          set { base[key] = value; }
        }
      }

      public class BIT
      {
        int N; long[] array;
        public BIT(int m) { for (int n = 1; ; n *= 2) { if (n >= m) { N = n; array = new long[N + 1]; break; } } }
        public void Add(int idx, int v) { for (int x = idx; x <= N; x += x & -x) { array[x] += v; } }
        public long Sum(int idx) { long ret = 0; for (int x = idx; x > 0; x -= x & -x) { ret += array[x]; } return ret; }
      }
    }
    struct MOD
    {
      public static long P = 1000000007;
      public readonly long V;

      public MOD(long a) { this.V = a % P; }
      public static implicit operator MOD(long a) { return new MOD(a); }
      public static MOD operator +(MOD a, MOD b) { return new MOD((a.V + b.V) % P); }
      public static MOD operator -(MOD a, MOD b) { return new MOD((a.V - b.V + P) % P); }
      public static MOD operator *(MOD a, MOD b) { return new MOD((a.V * b.V) % P); }
      public static MOD operator /(MOD a, MOD b) { return new MOD((a.V * b.Inverse().V) % P); }
      public MOD Inverse()
      {
        long a = V, p = P; long b = p, c = 1, d = 0, e = 0, f = 0;
        while (b != 0) { e = a / b; f = b; b = a - e * b; a = f; f = d; d = c - e * d; c = f; }
        c %= p;
        return c + (c < 0 ? p : 0);
      }
      public MOD Power(long n)
      {
        long a = V, p = P; long res = 1; long mult = a;
        for (int i = 0; i < 63; ++i) { if ((n & ((long)1 << i)) > 0) { res = (res * mult) % p; } mult = (mult * mult) % p; }
        return res;
      }
      public override string ToString() { return V.ToString(); }
    }


    static class Read
{
static Queue<string> queue = new Queue<string>();
static void Enqueue() { var ss = Console.ReadLine().Split(' '); foreach (var s in ss) { queue.Enqueue(s); } }
public static int Int() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt32(queue.Dequeue()); }
public static long Long() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt64(queue.Dequeue()); }
public static string Str() { if (queue.Count == 0) { Enqueue(); } return queue.Dequeue(); }
public static int[] IntN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray(); }
public static long[] LongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray(); }
public static ulong[] ULongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToUInt64(s)).ToArray(); }
public static string[] StrN() { return Console.ReadLine().Split(' '); }
public static Tuple<int, int>[] TupleInt(int n) { List<Tuple<int, int>> list = new List<Tuple<int, int>>(); for (int i = 0; i < n; ++i) { var ab = Read.IntN(); list.Add(new Tuple<int, int>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<long, long>[] TupleLong(int n) { List<Tuple<long, long>> list = new List<Tuple<long, long>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<long, long>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<string, string>[] TupleStr(int n) { List<Tuple<string, string>> list = new List<Tuple<string, string>>(); for (int i = 0; i < n; ++i) { var ab = Read.StrN(); list.Add(new Tuple<string, string>(ab[0], ab[1])); } return list.ToArray(); }
public static Tuple<double, double>[] TupleDouble(int n) { List<Tuple<double, double>> list = new List<Tuple<double, double>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<double, double>(ab[0], ab[1])); } return list.ToArray(); }
public static long[,] LongMatrix(int r, int c) { var mat = new long[r, c]; for (int i = 0; i < r; ++i) { var x = Read.LongN(); for (int j = 0; j < c; ++j) { mat[i, j] = x[j]; } } return mat; }
public static Dictionary<int, HashSet<int>> AdjacencyList(int N, int M, bool isDirectional = false)
{
Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
for (int i = 0; i <= N; ++i) { dict.Add(i, new HashSet<int>()); }
for (int i = 0; i < M; ++i) { var ab = Read.IntN(); if (!dict[ab[0]].Contains(ab[1])) { dict[ab[0]].Add(ab[1]); } if (!isDirectional && !dict[ab[1]].Contains(ab[0])) { dict[ab[1]].Add(ab[0]); } }
return dict;
}
public static Dictionary<int, Dictionary<int, long>> AdjacencyListWithWeight(int N, int M, bool isDirectional = false)
{
Dictionary<int, Dictionary<int, long>> dict = new Dictionary<int, Dictionary<int, long>>(); for (int i = 0; i <= N; ++i) { dict.Add(i, new Dictionary<int, long>()); }
for (int i = 0; i < M; ++i) { var ab = Read.IntN(); dict[ab[0]].Add(ab[1], ab[2]); if (!isDirectional) { dict[ab[1]].Add(ab[0], ab[2]); } }
return dict;
}
}
    }
}


Measured memory_bytes: 18044