Codeforces 1A (A. Theatre Square) Simple math problem

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

A simple math problem! But I was wrong 2 times at first.

Learned: 1 I learn how to use the function of "ceil".   eg:    ceil(4.3)=5;

2 If the problem's data need to use the "__int64" type,you'd better insure  the relational data use the "__int64" type too,or you may wrong easily!

For this problem,I first submission was wrong because the data 'x' and 'y' are 'int', I should use the "__int64":

View Code

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
int m,n,a;
__int64 x,y;
__int64 sum;
while(cin>>m>>n>>a)
{
if(m%a==0)
x=m/a;
else
x=m/a+1;
if(n%a==0)
y=n/a;
else
y=n/a+1;
sum=x*y;
printf("%I64d\n",sum);

}
return 0;
}