let pyramides n tab =
  for flr = n - 2 downto 0 do
    for i = 0 to flr do
      tab.(flr).(i) <- tab.(flr).(i) + max tab.(flr+1).(i) tab.(flr+1).(i+1)
    done
  done;
  tab.(0).(0)

let _ =
    let n = read_int () in
    let numbers = Array.init n
                             (fun k -> Array.init (k+1)
                                                  (fun _ -> Scanf.scanf "%d "
                                                                        (fun x -> x)))
    in print_int (pyramides n numbers);
       print_newline ()