open Num
let rec f n =
  let rec aux m x y = match m with
      _ when n < m -> y
    | 0 -> aux (m + 1) y (num_of_int 4)
    | 1 -> aux (m + 1) y (num_of_string "17/4")
    | _ -> aux (m + 1) y ((num_of_int 108) -/ (num_of_int 815) // y +/ (num_of_int 1500) // (y */ x))
  in aux 0 (num_of_int 0) (num_of_int 0)
let (<<) f g x = f (g x)
let println = print_newline << print_string << approx_num_fix 30
let () =
  println @@ f 0;
  println @@ f 1;
  println @@ f 2;
  println @@ f 3;
  println @@ f 80;
 

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