NEFU要崛起——第1场 A - Theatre Square

Description
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 Input
Input
6 6 4
Output
4
很简单的题目，告诉了一个广场的长和宽，要铺地板，告诉了地板的长（正方形），地板不能打碎，问至少多少地板能铺满广场。需要注意一点，int型太小，需要__int64.

#include <iostream>using namespace std;int main(){__int64 a,m,n,mm,nn;while(cin>>m){cin>>n>>a;    mm=m/a;    if(m%a!=0)    mm++;   nn=n/a;   if(n%a!=0)   nn++;   cout<<mm*nn<<endl;}return 0;}