Scanf.scanf "%d" (fun n ->
    let rec loop_a a acc =
        let rec loop_b b acc =
            if a * b >= n then loop_a (a + 1) acc else
                loop_b (b + 1) (acc + 1)
        in
        if a >= n then acc else loop_b 1 acc
    in
    loop_a 1 0 |> Printf.printf "%d\n"
)