let read () = Scanf.scanf "%s %s %s " (fun x y _ -> x, y)

let () =
  let sa, pa = read () in
  let sb, pb = read () in
  print_endline
    (if pa = pb then "-1"
     else if String.length pa > String.length pb then sa
     else if String.length pa < String.length pb then sb
     else if pa > pb then sa else sb)