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