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 b = Array.of_list (split (read_line ())) in
        let r = Array.make n 0 in
        r.(0) <- b.(0);
        r.(n - 1) <- b.(n - 2);
        for i = 0 to n - 3 do
            r.(i + 1) <- min b.(i) b.(i + 1)
        done;
        Printf.printf "%d\n" (Array.fold_left (+) 0 r)
    in
    main ()