CodeForces 1A and tutorial in http://algocoding.wordpress.com/2013/03/09/codeforces-tutorial-1-introduction/

gistfile1.cpp

#include <iostream>
using namespace std;

int main() {
    long long int n;
    long long int m;
    long long int a;
    
    cin >> n;
    cin >> m;
    cin >> a;
    
    long long int titles1 = n/a;
    long long int titles2 = m/a;
    
    if (n%a != 0) titles1++;
    if (m%a != 0) titles2++;
    
    long long int result = titles1*titles2;
    cout << result;
    
    return 0;
}