open Num

let read_sp () =
  let s, p = read_line () |>
             Str.split (Str.regexp_string " ") |>
             fun lst -> (List.nth lst 0, Num.num_of_string (List.nth lst 1))
  in
  (s, p)

let solve (sa, pa) (sb, pb) =
  if pa =/ pb then "-1"
  else if pa >/ pb then sa
  else sb

let () =
  let sa, pa = read_sp ()
  and sb, pb = read_sp ()
  in
  solve (sa, pa) (sb, pb) |> print_endline