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 Fortran (GNU Fortran 9.2.1) (judge verdict: Wrong Answer)

program prob5
    implicit none
    integer(8) :: n, k
    integer(8) :: ans
    read(*,*) n, k
    ans = 0
    if(mod(k , 2) == 0) then
        ans = (N/K) * (N/K) * (N/K)
        ans = ans + ((N/(K/2))+1)/2 * ((N/(K/2))+1)/2 * ((N/(K/2))+1)/2
    else
        ans = (N/K) * (N/K) * (N/K)
    end if
    write(*,*) ans
    stop
contains
end program prob5