open Hashtbl
let n = Scanf.scanf " %d" @@ (+) 0
let ws = Array.init n @@ fun _ -> Scanf.scanf " %s" @@ fun s -> s
let h = create n
let rec check i c =
  if i >= n then true
  else
    let w = ws.(i) in
    if w.[0] <> c then false
    else if mem h w then false
    else (add h w 1; check (i + 1) w.[String.length w - 1])
let _ = print_endline @@ if check 0 ws.(0).[0] then "Yes" else "No"