#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, c, count;
  cin >> a >> b >> c;
  for (long long int i = (long long int)(a); i < (long long int)(b); i++) {
    if (i % c == 0) count++;
  }
  cout << count << "\n";
  return 0;
}
