#include <bits/stdc++.h>
int main() {
  int a, b, c, i = 0;
  scanf("%d\n %d\n %d\n", &a, &b, &c);
  if (1 <= a && c <= 10000 && a <= b) {
    for (int k = a; k <= b; k++) {
      if (k % c == 0) {
        i++;
      }
    }
  }
  printf("%d\n", i);
  return 0;
}
