open Batteries
(* a = (N - C) / B *)
let n = read_int ()


let rec a_loop a result_a =
  let rec b_loop b result_b =
    if a * b >= n then result_b else b_loop (b+1) (result_b+1)
  in if a >= n then result_a else a_loop (a+1) (result_a + (b_loop 1 0))


let () = Printf.printf "%d\n" @@ a_loop 1 0
