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