以下附代码

#include <bits/stdc++.h>
using namespace std;

int main()
{
	long a,n,m,square,brick,lengh=0,wide=0;
	cin>>n>>m>>a;
	square=n*m;
	brick=a*a;
	lengh=n/a;
	wide=m/a;
	if(n%a!=0)
	   lengh++;
	if(m%a!=0)
	   wide++;
	cout<<lengh*wide; 
	return 0;
}