output_description: If every word announced by Takahashi satisfied the conditions, print `Yes`;
  otherwise, print `No`.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      W_1
      W_2
      :
      W_N
attempt: 3
  abc
  arc
  agc
  
problem_description: Statement
  
  Takahashi is practicing _shiritori_ alone again today.
  
  Shiritori is a game as follows:
  
    * In the first turn, a player announces any one word.
    * In the subsequent turns, a player announces a word that satisfies the following conditions:
      * That word is not announced before.
      * The first character of that word is the same as the last character of the last word announced.
  
  In this game, he is practicing to announce as many words as possible in ten
  seconds.
  
  You are given the number of words Takahashi announced, N, and the i-th word he
  announced, W_i, for each i. Determine if the rules of shiritori was observed,
  that is, every word announced by him satisfied the conditions.
samples: [{"input": "4\n    hoge\n    english\n    hoge\n    enigma", "output": "No\n    \n\nAs `hoge` is announced multiple times, the rules of shiritori was not\nobserved.\n\n* * *"}, {"input": "9\n    basic\n    c\n    cpp\n    php\n    python\n    nadesico\n    ocaml\n    lua\n    assembly", "output": "Yes\n    \n\n* * *"}, {"input": "8\n    a\n    aa\n    aaa\n    aaaa\n    aaaaa\n    aaaaaa\n    aaa\n    aaaaaaa", "output": "No\n    \n\n* * *"}, {"input": "3\n    abc\n    arc\n    agc", "output": "No"}]