(* Returns a line from stdin, or "^D" if EOF                 *)
let get_line () =
  try 
    read_line ()                     (* read a line          *)
    with End_of_file -> "\004"       (* assume ^D marks EOF  *)
;;

(* Counts # lines from stdin                                 *)
let rec count_lines () =
   let line = (get_line ()) in       (* get a line           *)
     if (line.[0] = '\004') then 0   (* if EOF then 0 lines  *)
     else 1+count_lines()            (* else read more lines *)
;;

print_int ( count_lines () ) ; print_endline ""
;;