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)

N, K = map(int, input().split())

count = 0
for a in range(1, N+1):
    # b, c in range(K - (a % K), N+1, K)
    # b + c == (i + j) * K - 2 * (a % K)
    # (2 * a) % K == 0

    if (2 * a) % K != 0:
        continue

    min_b = K - (a % K)
    n_b   = (N + K - min_b) // K
    count += n_b ** 2

print(count)