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.

Sample test(s)

input

6 6 4

output

4

题目是用正方形(a*a)的瓷砖铺广场（m*n的矩形）  一定要铺满，可以有多出来的不过尽可能少。。

实质是，求上整数问题：  up(a/b) = ((a  + b -1) / b)

代码很短（python的特点）：

n,m,a = [int(s) for s in raw_input().split()]print ((n+a-1)/a)*((m+a-1)/a)