let () =
    let split s =
        let rec loop i cur flag acc =
            if i = String.length s then ( if flag then cur :: acc else acc) else (
                match flag, s.[i] with
                | true,  ' ' -> loop (i + 1) "" false (cur :: acc)
                | false, ' ' -> loop (i + 1) "" false acc
                | true,  v   -> loop (i + 1) (Printf.sprintf "%s%c" cur v) true acc
                | false, v   -> loop (i + 1) (Printf.sprintf "%s%c" cur v) true acc
            )
        in
        List.map int_of_string (List.rev (loop 0 "" false []))
    in
    let main () =
        let n = int_of_string (read_line ()) in
        let h = split (read_line ()) in
        let rec loop prev = function
            | [] -> "Yes"
            | hd :: tl -> if hd > prev + 1 then "No" else
                          if hd = prev + 1 then loop (hd - 1) tl else
                              loop hd tl
        in
        match List.rev h with
        | hd :: tl -> print_endline (loop hd tl)
        | [] -> failwith "??"

    in
    main ()