(defn Shiritori [Ws]
  (if-not (= (count Ws) (-> Ws distinct count))
    "No"
    (if 
      (->> Ws 
        (map #(list (first %) (last %))) 
        (apply concat) 
        rest 
        (partition 2)
        (map distinct) 
        (map count) 
        (every? #(= 1 %)))
      "Yes"
      "No"
  )))
(defn input [N]
  (if (zero? N) 
    '()
    (cons (read-line) (input (dec N)))))


(-> (Integer/parseInt (read-line))
  input
  Shiritori
  println)