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
问题简述：
输入一个广场的长跟宽，输入正方形砖块的长度，求要多少块砖块才可以铺满广场。注：砖块不能切割。
问题分析：
用长宽分别除以砖块长度，即可得到数量，然后分别取余，若不为0，砖块长宽分别加一。
程序说明：
使用__int64 定义64位整数。
AC的C++程序如下：
#include<iostream>
using namespace std;
int main()
{
__int64 n, m, a,b,c;
cin >> n >> m >> a;
b = n / a;
c = m / a;
if (n%a) b++;
if (m %a)c++;
cout << b * c;
return 0;
}