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