#include <bits/stdc++.h>
int main() {
  int a, b, c, count;
  count = 0;
  std::cin >> a;
  std::cin >> b;
  std::cin >> c;
  for (; a <= b; a++) {
    if (a % c == 0) {
      count++;
    }
  }
  if (a > b) {
    std::cout << count << std::endl;
  }
  return 0;
}
