#include <bits/stdc++.h>
int main(int argv, char *argc[]) {
  int a, b, c;
  int buf, count, roop;
  scanf("%d %d %d", &a, &b, &c);
  for (roop = 0;; roop++) {
    if ((a <= (c * roop)) && (b >= (c * roop))) {
      count++;
      if (b <= (c * roop)) break;
    }
  }
  printf("%d\n", count);
  return 0;
}
