GZHU18级第二次周赛——白银等级 A - Problem A CodeForces - 1A

*Time limit :1000 ms
Memory limit ：262144 kB
Source ：Codeforces Beta Round #1
Tags ：math 1300
Editorial ：Announcement Tutorial #1 Tutorial #2

问题描述 ：
Theatre Square in the capital city of Berland has a rectangular shape with the size n × m meters. On the occasion of the city’s anniversary, a decision was taken to pave the Square with square granite flagstones. Each flagstone is of the size a × a.

What is the least number of flagstones needed to pave the Square? It’s allowed to cover the surface larger than the Theatre Square, but the Square has to be covered. It’s not allowed to break the flagstones. The sides of flagstones should be parallel to the sides of the Square.

Input
The input contains three positive integer numbers in the first line: n,  m and a (1 ≤  n, m, a ≤ 109).

Output
Write the needed number of flagstones.

Examples
Input
6 6 4
Output
4

#include <iostream>
using namespace std;
int main()
{
 double n, m, a;
long long C,D;
	cin >> n >> m >> a;
	C = n / a;
	D = m / a;
	if (C<n/a)
	{
		C+= 1;
	}
	if (D< m/a) 
	{
		D += 1;
	}
	cout <<C*D;
	return 0;
}