Problem:
Score : 300 points

Problem Statement

You are given integers N and K. Find the number of triples (a,b,c) of positive integers not greater than N such that a+b,b+c and c+a are all multiples of K.
The order of a,b,c does matter, and some of them can be the same.

Constraints

1 \leq N,K \leq 2\times 10^5

N and K are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the number of triples (a,b,c) of positive integers not greater than N such that a+b,b+c and c+a are all multiples of K.

Sample Input 1

3 2

Sample Output 1

9

(1,1,1),(1,1,3),(1,3,1),(1,3,3),(2,2,2),(3,1,1),(3,1,3),(3,3,1) and (3,3,3) satisfy the condition.

Sample Input 2

5 3

Sample Output 2

1

Sample Input 3

31415 9265

Sample Output 3

27

Sample Input 4

35897 932

Sample Output 4

114191

Solution in PyPy3 (2.4.0) (judge verdict: Accepted)

import sys
import math  # noqa
import bisect  # noqa
import queue  # noqa


def input():
    return sys.stdin.readline().rstrip()


def main():
    N, K = map(int, input().split())

    num = [0 for _ in range(K)]
    for i in range(1, N + 1):
        num[i % K] += 1

    res = 0
    for a in range(0, K):
        b = (K - a) % K
        c = (K - a) % K
        if (b + c) % K != 0:
            continue
        res += num[a] * num[b] * num[c]

    print(res)


if __name__ == '__main__':
    main()