#include <bits/stdc++.h>
int main(void) {
  int aa, bb, cc, i, num;
  scanf("%d %d %d", &aa, &bb, &cc);
  num = 0;
  for (i = aa; i <= bb; i++) {
    if ((i % cc) == 0) {
      num++;
    }
  }
  printf("%d\n", num);
  return 0;
}
