#include <bits/stdc++.h>
int main() {
  int a, b, c, i;
  i = 0;
  scanf("%d%d%d", &a, &b, &c);
  while (a <= b) {
    if (a % c == 0) {
      i++;
    }
    a++;
  }
  printf("%d", i);
  return 0;
}
