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 Python (3.8.2) (judge verdict: Wrong Answer)

# import sys
# import math #sqrt,gcd,pi
# import decimal
# import queue # queue
# import bisect
# import heapq # priolity-queue
# import time
# from itertools import product,permutations,\
    # combinations,combinations_with_replacement
# 重複あり順列、順列、組み合わせ、重複あり組み合わせ
# import collections # deque
# from operator import itemgetter,mul
# from fractions import Fraction
# from functools import reduce

mod = int(1e9+7)
# mod = 998244353
INF = 1<<50

def readInt():
    return list(map(int,input().split()))

def main():
    x,k,d = readInt()
    count = x // d
    mn = 0
    if count>k:
        mn = x - (d * k)
    else:
        mn = x % d
    ans = INF
    if (k-count)%2==0:
        ans = mn
    else:
        ans = abs(mn-d)
    print(ans)
    return

if __name__=='__main__':
    main()