#include <iostream>
 
using namespace std;
 
int main()
{
    int i,n,k;
    double p;
    p=1;
    cout<<"Od broja?"<<endl;
    cin>>k;
    cout<<"Do broja?"<<endl;
    cin>>n;
    i=k;
    while (i<=n )
    {
      if (i%3==0)
        p=p*i;
      i++;
    }
    cout<<"Produkt iznosi: "<<p<<endl;
  
    return 0;
}