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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.io.*;
import java.util.*;
public class Main {
    static long startTime;
    static long endTime;
    static Boolean [] prime ;
    static int M=(int)1e9+7;
    static class FastReader{
        BufferedReader br;
        StringTokenizer st;

        public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next()
        {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException  e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt()
        {
            return Integer.parseInt(next());
        }

        long nextLong()
        {
            return Long.parseLong(next());
        }

        double nextDouble()
        {
            return Double.parseDouble(next());
        }

        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
    static void yes(){
        System.out.println("YES");
    }
    static void no(){
        System.out.println("NO");
    }
    public static int lowerBound
            (Integer[] array, int length, int value) {
        int l = 0;
        int r = length;
        while (l < r) {
            int mid = (l + r) / 2;
            if (value < array[mid]) {
                r = mid;
            } else {
                l = mid + 1;
            }
        }
        return l;
    }
    public static long gcd(long a, long b){
        if (b == 0)
            return a;
        else return gcd(b, a % b);
    }
    public  static  long countDivs(long n ){
        int cn=0;
        long sqr = (long)Math.sqrt(n);
        for (long i = 1; i<=sqr ; ++i) {
            if(n%i==0){
                ++cn;
            }
        }
        cn*=2;
        if(sqr*sqr==n) cn--;
        return cn;

    }
    static void prime(int  x) {
        //sieve algorithm. nlog(log(n)).
        prime=new Boolean[ (x+1)];
        Arrays.fill(prime,true);
        prime[0] = prime[1] = false;
        for (int  i = 2; i * i <= x ; i++)
            if (prime[i])
                for (int  j = i * i; j <= x; j += i)
                    prime[j] = false;
    }
    static int[] sum;
    static void cumulitiveSum( int [] arr){
        sum = new int[arr.length];
        sum[0]=arr[0];
        for (int i = 1; i <arr.length; i++) {
            sum[i]=arr[i]+sum[i-1];
        }
    }
    static boolean isEven(long x ){
        return x % 2 == 0;
    }
    static boolean isPrime(long x ){
        boolean flag = true;
        int sqr = (int)Math.sqrt(x);
        if(x<2) return false;
        for (int i = 2; i <=sqr; i++) {
            if(x%i==0){
                flag=false;
                break;
            }
        }
        return flag;
    }
    static long factorial( long x) {
        long total = 1;
        for (int i = 2; i <= x; i++)
            total *= i;
        return total;
    }
    static long power(long x, long n) {
        if (n == 0) {
            return 1;
        }

        long pow = power(x, n / 2L);
        if ((n & 1) == 1) {
            return x * pow * pow;
        }

        return pow * pow;
    }

    public static void main(String [] args) {
        startTime = System.currentTimeMillis();
       // int T = sc.nextInt();while (T--!=0)
        {
            solve();
        }
        endTime = System.currentTimeMillis();
        long duration= endTime-startTime;
        //System.out.println(duration);
    }

    //  static Scanner sc = new Scanner(System.in);
    static FastReader sc = new FastReader();
    public static void solve()  {
//////////////////////////////////////////////////////////////////////
    long x= sc.nextLong();
    long k=sc.nextLong(),d=sc.nextLong();
    x=Math.abs(x);
    long temp=x/d;
    long best =Math.abs(x-temp*d);

    if(temp>k){
        System.out.println(Math.abs(x-k*d));
    }
    else if(temp==k) System.out.println(best);
    else {
        long y=k-temp;
        if(y%2==0){
            System.out.println(best);
        }
        else {
            if(best>=0){
                System.out.println(Math.abs(best-d));
            }
            else System.out.println(best+d);
        }

    }
///////////////////////////////////////////////////////////////////////
    }

}