l, r, n = map(int, input().split()) if n == 1: print(r - l + 1) exit() if l % n == 0: ll = l else: ll = l + n - l % n if r % n == 0: rr = r - 1 else: rr = r - r % n - 1 base = ((rr + 1) - l) // n ln = l % n rn = r % n for i in range(n): x = base if i >= ln: x += 1 if i <= rn: x += 1 print(x)