//#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
int a, b, c, k;
cin >> a >> b >> c;
k = 0;
for (int i = 0; i >= b; i += c)
{
if ((i >= a) && (i <= b)) k+=1;
}
cout << k;
return 0;
}
Ly8jaW5jbHVkZSAic3RkYWZ4LmgiCiNpbmNsdWRlIDxpb3N0cmVhbT4KdXNpbmcgbmFtZXNwYWNlIHN0ZDsKIAppbnQgbWFpbigpCnsKICAgIGludCBhLCBiLCBjLCBrOwogICAgY2luID4+IGEgPj4gYiA+PiBjOwogICAgayA9IDA7CiAgICBmb3IgKGludCBpID0gMDsgaSA+PSBiOyBpICs9IGMpCiAgICB7CiAgICAgICAgaWYgKChpID49IGEpICYmIChpIDw9IGIpKSBrKz0xOwogICAgfQogICAgY291dCA8PCBrOwogICAgcmV0dXJuIDA7Cn0=