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 Python (3.4.3) (judge verdict: Accepted)

# -*- coding: utf-8 -*-
import sys
import math
from bisect import bisect_left
from bisect import bisect_right
import collections
input = sys.stdin.readline

# bisect_left(lists, 3)
# bisect_right(lists, 3)

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

	ans = 0
	ans2 = 0
	for i in range(1, N+1):
		if i % K == 0:
			#print(i)
			ans += 1
		elif K % 2 == 0 and i % K == K/2:
			#print(i)
			ans2 += 1
	
	print(ans*ans*ans + ans2*ans2*ans2)

	
	
if __name__ == "__main__":
	main()