蒟蒻的无奈

#include<bits/stdc++.h>
using namespace std;
int n,m,a,x,y;
int main(){
	cin>>n>>m>>a;
	if(n%a==0) x=n/a;
	else x=n/a+1;
	if(m%a==0) y=m/a;
	else y=m/a+1;
	cout<<x*y;
	return 0;
}

Who cam help me??