C :

#include<stdio.h>
int main()
{
    long int n,m,a,s;
    while(~scanf("%ld%ld%ld",&n,&m,&a))
    {
        s=((m+a-1)/a)*((n+a-1)/a);
        printf("%ld\n",s);
    }
   return 0;
}

C++ :

#include<cstdio>
#include<iostream>
#include<cmath>

using namespace std;

int main()
{
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    long long n, m, a;
    while(cin >> n >> m >> a)
    {
        long long tn = (n % a == 0 ? n / a : n / a + 1);
        long long tm = (m % a == 0 ? m / a : m / a + 1);
        cout << tn * tm << endl;
    }
    return 0;
}