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 C (GCC 9.2.1) (judge verdict: Wrong Answer)

#include<stdio.h>
long long  move(long long  a ,long long  b){
	long long  plus=a+b;
    long long  gausplus;
    long long  minus=a-b;
    long long  gausminus;
  if(plus<0){
    gausplus=plus*(-1);
  }
  if(minus<0){
    gausminus=minus*(-1);
  }
  if(gausplus>gausminus){
    return plus;
  }else{
   	return minus;
  }
}

int main(void){
  long long  X;
  long long  K;
  long long  D;
  long long  place;
  scanf("%ld",&X);
  scanf("%ld",&K);
  scanf("%ld",&D);
  long long i;
  place=X;
 
  for(i=0;i<K;i++){
  	place=move(place,D);
  }
  if(place<0){
    place=place*(-1);
  }
  printf("%ld",place);
}