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;
    $half_count = ((int($N) - int($half_first)) / int($K)) + 1;
#    $half_count = 1;
#    while (1) {
#        $half_first += $K;
#        if ($half_first <= $N) {
#            $half_count++;
#            next;
#        } else {
#            last;
#        }
#    }
}
 
my $bingo;
{
    $a = $N % $K;
    $bingo = ($N - $a) / $K;
}
 
say $half_count ** 3 + $bingo ** 3;
 
__END__
 
7*11*1483
 
114191 - 54872