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)

N, K = [int(i) for i in input().split()]
cnt = 0
if K % 2 == 0:
    for i in range(1, 2*N//K+1):
        cnt += 1 + (2*N//K-i)//2 * 6 + (2*N//K-i)//2 * ((2*N//K-i)//2 - 1) * 3
else:
    for i in range(1, N//K+1):
        cnt += 1 + (N//K-i) * 6 + (N//K-i) * ((N//K-i) - 1) * 3

print(cnt)