object Main {
  def main(args: Array[String]) {
    var check = true
    var count = 0
    var words = Array[String]()
    for(line <- io.Source.stdin.getLines()) {
      if(count == 0) {

      }
      else if(count == 1)
      {
        words = words :+ line
      }
      else{
        val start_char = words(count - 2)(words(count - 2).length - 1)
        if (start_char != line(0)) {
          check = false
        }

        for( c <- words ) {
          if(line == c) {
            check = false
          }
        }

        words = words :+ line
      }
      count += 1
    }

    if(check){
      println("Yes")
    }
    else {
      println("No")
    }
  }
}
