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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <cstdio> 
using namespace std;

const int maxn=25;
int l, n, src, dst, m;

int main(){
	scanf("%d", &l);
	for (int i=l+1; i; i>>=1) ++n;
	m=n*2-2;
	for (int i=21; i>=0; --i) if ((l-(1<<n-1)+1)&(1<<i)) ++m;
	printf("%d %d\n", n, m);
	src=n; dst=1; int t=1;
	for (int i=1; i<n; ++i, t*=2) 
		printf("%d %d %d\n", i+1, i, t);
	int nowe=(1<<(n-1)); l=l-nowe;
	while (l>=0){
		for (t=21; t>=0; --t) if (l-(1<<t)>=-1) break;
		printf("%d %d %d\n", src, t+1, nowe);
		nowe+=(1<<t); l-=(1<<t);
	}
	return 0;
}