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