let () =
  let n = Scanf.scanf "%d " (fun i -> i) in
  let a = Array.make_matrix n n false in
  for i = 0 to n - 1 do
    for j = 0 to n - 1 do
      let x = Scanf.scanf "%s " (fun i -> i) in
      a.(i).(j) <- x = "-" || x = "nyanpass"
    done
  done;
  let rec doit i j =
    if i = n then true
    else a.(i).(j) && doit (i + 1) j in
  let doit j = doit 0 j in
  let rec loop j lst =
    if j = n then lst
    else loop (j + 1) (if doit j then j :: lst else lst) in
  let loop () = loop 0 [] in
  match loop () with
  | [j] -> Printf.printf "%d\n" (j + 1)
  | _ -> Printf.printf "%d\n" (-1)