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

namespace AtCoder {
    public class TestCode {
        static void Main(string[] args) {
            var (X,K,D) = ReadValue<long,long,long>();
            long ans = 0;
            var tmp = Math.Abs(X) / D;
            if (tmp > K) ans = Math.Abs(X) - (K * D);
            else {
                var t = Math.Abs(X) - (tmp * D);
                if((K - tmp) % 2 == 0) {
                    ans = t;
                } else {
                    ans = t - D;
                }
            }
            Console.Write(Math.Abs(ans));
        }

        static T1 ReadValue<T1>() {
            var t1 = TypeDescriptor.GetConverter(typeof(T1));
            return (T1)t1.ConvertFromString(Console.ReadLine());
        }

        static (T1, T2) ReadValue<T1, T2>() {
            var rl = Console.ReadLine().Trim().Split().ToArray();
            var t1 = TypeDescriptor.GetConverter(typeof(T1));
            var t2 = TypeDescriptor.GetConverter(typeof(T2));
            return ((T1)t1.ConvertFromString(rl[0]),
                    (T2)t2.ConvertFromString(rl[1]));
        }

        static (T1, T2, T3) ReadValue<T1, T2, T3>() {
            var rl = Console.ReadLine().Trim().Split().ToArray();
            var t1 = TypeDescriptor.GetConverter(typeof(T1));
            var t2 = TypeDescriptor.GetConverter(typeof(T2));
            var t3 = TypeDescriptor.GetConverter(typeof(T3));
            return ((T1)t1.ConvertFromString(rl[0]),
                    (T2)t2.ConvertFromString(rl[1]),
                    (T3)t3.ConvertFromString(rl[2]));
        }

        static (T1, T2, T3, T4) ReadValue<T1, T2, T3, T4>() {
            var rl = Console.ReadLine().Trim().Split().ToArray();
            var t1 = TypeDescriptor.GetConverter(typeof(T1));
            var t2 = TypeDescriptor.GetConverter(typeof(T2));
            var t3 = TypeDescriptor.GetConverter(typeof(T3));
            var t4 = TypeDescriptor.GetConverter(typeof(T4));
            return ((T1)t1.ConvertFromString(rl[0]),
                    (T2)t2.ConvertFromString(rl[1]),
                    (T3)t3.ConvertFromString(rl[2]),
                    (T4)t4.ConvertFromString(rl[3]));
        }

        static (T1, T2, T3, T4, T5) ReadValue<T1, T2, T3, T4, T5>() {
            var rl = Console.ReadLine().Trim().Split().ToArray();
            var t1 = TypeDescriptor.GetConverter(typeof(T1));
            var t2 = TypeDescriptor.GetConverter(typeof(T2));
            var t3 = TypeDescriptor.GetConverter(typeof(T3));
            var t4 = TypeDescriptor.GetConverter(typeof(T4));
            var t5 = TypeDescriptor.GetConverter(typeof(T5));
            return ((T1)t1.ConvertFromString(rl[0]),
                    (T2)t2.ConvertFromString(rl[1]),
                    (T3)t3.ConvertFromString(rl[2]),
                    (T4)t4.ConvertFromString(rl[3]),
                    (T5)t5.ConvertFromString(rl[4]));
        }

        static string[] stringArray => Console.ReadLine().Split().ToArray();
        static int[] intArray => Console.ReadLine().Trim().Split().Select(int.Parse).ToArray();
        static long[] longArray => Console.ReadLine().Trim().Split().Select(long.Parse).ToArray();
        static double[] doubleArray => Console.ReadLine().Trim().Split().Select(double.Parse).ToArray();
        static decimal[] decimalArray => Console.ReadLine().Trim().Split().Select(decimal.Parse).ToArray();
    }
}


Measured memory_bytes: 30144