# CF解題紀錄 1A Theatre Square(水)

A. Theatre Square
time limit per test 2 seconds
memory limit per test 64 megabytes
input standard input
output standard output
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.

＊題意：給n*m的矩形 邊長為a的正方形 求最少需要多少塊正方形來鋪滿。
# 思路分析
將n、m分開來看，用長為a的線段來鋪上長為n、m的邊
例：n=6 m=4的矩形 和 a=2 的正方形 n線段需6/2=3塊 m線段需4/2=2塊
n*m即為所需正方型數量。

# 實作

#include<iostream>
using namespace std;
#define LL long long
int main(){
	int n,m,a;
	cin >> n >> m >> a;
	LL x=n%a==0?n/a:n/a+1;
	LL y=m%a==0?m/a:m/a+1;
	cout << x*y << endl;
}