解

#include<iostream>
using namespace std;
int main(){
    long long a,b,c;
    cin >> a >> b >> c;
    if(a%c==0)
        a/=c;
    else
        a = a/c+1;
    if(b%c==0)
        b/=c;
    else
        b = b/c+1;
    cout << a*b;
}