codeforces 1A Theatre Square（再来一水题）

A. Theatre Square
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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

分而治之的思想，其实就是直接看边长。不多说，上代码：

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
    long long int n,m,a;
   long long int ans;
    while(cin>>n>>m>>a)
    {
        //cout<<ceil(double(m)/a);
        ans=ceil(double(n)/a)*ceil(double(m)/a);
        cout<<ans<<endl;
    }
    return 0;
}