#include<fstream>
using namespace std;
int a,b,k,nr,i;
int main()
{
    ifstream f("pomi.in");
    ofstream g("pomi.out");
    f>>a;
    f>>b;
    f>>k;
    for(i=a;i<=b;i++)
    if(i%k==0)
    nr++;
    g<<nr;
    return 0;
}