public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  String [ ] [ ] nArray = new String [ n ] [ ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    String num = sc . next ( ) ;
    nArray [ i ] = num . split ( "" ) ;
  }
  boolean judge = true ;
  out : for ( int i = 1 ;
  i < n ;
  i ++ ) {
    for ( int k = 0 ;
    k < i ;
    k ++ ) {
      if ( Arrays . equals ( nArray [ i ] , nArray [ k ] ) ) {
        judge = false ;
        break out ;
      }
    }
  }
  for ( int i = 0 ;
  i < n - 1 ;
  i ++ ) {
    if ( nArray [ i ] [ nArray [ i ] . length - 1 ] . equals ( nArray [ i + 1 ] [ 0 ] ) ) {
    }
    else {
      judge = false ;
      break ;
    }
  }
  if ( judge ) {
    System . out . println ( "Yes" ) ;
  }
  else {
    System . out . println ( "No" ) ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) ; String [ ] [ ] nArray = new String [ n ] [ ] ; for ( int i = 0 ; i < n ; i ++ ) { String num = sc . next ( ) ; nArray [ i ] = num . split ( " " ) ; } boolean judge = true ; out : for ( int i = 1 ; i < n ; i ++ ) { for ( int k = 0 ; k < i ; k ++ ) { if ( Arrays . equals ( nArray [ i ] , nArray [ k ] ) ) { judge = false ; break out ; } } } for ( int i = 0 ; i < n - 1 ; i ++ ) { if ( nArray [ i ] [ nArray [ i ] . length - 1 ] . equals ( nArray [ i + 1 ] [ 0 ] ) ) { } else { judge = false ; break ; } } if ( judge ) { 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))) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (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)))) (local_variable_declaration type: (array_type element: (type_identifier) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (identifier)) dimensions: (dimensions)))) (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)))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (string_literal))))))) (local_variable_declaration type: (boolean_type) declarator: (variable_declarator name: (identifier) value: (true))) (labeled_statement (identifier) (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 (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 (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier)) (array_access array: (identifier) index: (identifier))))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement (identifier))))))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (method_invocation object: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (field_access object: (array_access array: (identifier) index: (identifier)) field: (identifier)) right: (decimal_integer_literal))) name: (identifier) arguments: (argument_list (array_access array: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) index: (decimal_integer_literal))))) consequence: (block) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (false))) (break_statement))))) (if_statement condition: (parenthesized_expression (identifier)) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal))))) alternative: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (string_literal))))))))