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 Perl (v5.18.2) (judge verdict: Wrong Answer)

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use 5.010;
my @args;
for (<>) {
    chomp $_;
    push @args, $_;
}

my ($N, $K) = split " ", shift @args;

my $half_count=0;
if ($K % 2 == 0) {
    my $half_first = $K / 2;
    $half_count = 1;
    while (1) {
        $half_first += $K;
        if ($half_first <= $N) {
            $half_count++;
            next;
        } else {
            last;
        }
    }
}

my $bingo = int($N / $K);

say $half_count ** 3 + $bingo ** 3;

__END__

7*11*1483

114191 - 54872