public static void main ( String [ ] args ) throws IOException {
  BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  int N = Integer . parseInt ( br . readLine ( ) ) ;
  List < String > sir = new ArrayList < String > ( ) ;
  boolean isCorrect = true ;
  String lastWord = "" ;
  for ( int n = 0 ;
  n < N ;
  n ++ ) {
    String word = br . readLine ( ) ;
    String [ ] chr = word . split ( "" ) ;
    if ( n == 0 ) lastWord = chr [ chr . length - 1 ] ;
    else {
      if ( ! lastWord . equals ( chr [ 0 ] ) ) {
        isCorrect = false ;
        break ;
      }
      else {
        if ( sir . contains ( word ) ) {
          isCorrect = false ;
          break ;
        }
        sir . add ( word ) ;
        lastWord = chr [ chr . length - 1 ] ;
      }
    }
    sir . add ( word ) ;
  }
  if ( isCorrect ) System . out . println ( "Yes" ) ;
  else System . out . println ( "No" ) ;
}

public static void main ( String [ ] args ) throws IOException { BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ; int N = Integer . parseInt ( br . readLine ( ) ) ; List < String > sir = new ArrayList < String > ( ) ; boolean isCorrect = true ; String lastWord = " " ; for ( int n = 0 ; n < N ; n ++ ) { String word = br . readLine ( ) ; String [ ] chr = word . split ( " " ) ; if ( n == 0 ) lastWord = chr [ chr . length - 1 ] ; else { if ( ! lastWord . equals ( chr [ 0 ] ) ) { isCorrect = false ; break ; } else { if ( sir . contains ( word ) ) { isCorrect = false ; break ; } sir . add ( word ) ; lastWord = chr [ chr . length - 1 ] ; } } sir . add ( word ) ; } if ( isCorrect ) System . out . println ( " Yes " ) ; else System . out . println ( " No " ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) (throws (type_identifier)) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))) (local_variable_declaration type: (generic_type (type_identifier) (type_arguments (type_identifier))) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (generic_type (type_identifier) (type_arguments (type_identifier))) arguments: (argument_list)))) (local_variable_declaration type: (boolean_type) declarator: (variable_declarator name: (identifier) value: (true))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (string_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (array_type element: (type_identifier) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (string_literal))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) consequence: (expression_statement (assignment_expression left: (identifier) right: (array_access array: (identifier) index: (binary_expression left: (field_access object: (identifier) field: (identifier)) right: (decimal_integer_literal))))) alternative: (block (if_statement condition: (parenthesized_expression (unary_expression operand: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (decimal_integer_literal)))))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement)) alternative: (block (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (expression_statement (assignment_expression left: (identifier) right: (array_access array: (identifier) index: (binary_expression left: (field_access object: (identifier) field: (identifier)) right: (decimal_integer_literal))))))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) (if_statement condition: (parenthesized_expression (identifier)) consequence: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal)))) alternative: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal)))))))