public static void main ( String args [ ] ) {
  Scanner s = new Scanner ( System . in ) ;
  int n = Integer . parseInt ( s . nextLine ( ) ) ;
  String prevWord = null ;
  String currWord = null ;
  Set < String > set = new HashSet < > ( ) ;
  boolean isValid = true ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    currWord = s . nextLine ( ) ;
    if ( set . contains ( currWord ) ) {
      isValid = false ;
    }
    set . add ( currWord ) ;
    if ( isValid && i != 0 ) {
      if ( prevWord . charAt ( prevWord . length ( ) - 1 ) != currWord . charAt ( 0 ) ) {
        isValid = false ;
      }
    }
    prevWord = currWord ;
  }
  System . out . println ( isValid ? "Yes" : "No" ) ;
}

public static void main ( String args [ ] ) { Scanner s = new Scanner ( System . in ) ; int n = Integer . parseInt ( s . nextLine ( ) ) ; String prevWord = null ; String currWord = null ; Set < String > set = new HashSet < > ( ) ; boolean isValid = true ; for ( int i = 0 ; i < n ; i ++ ) { currWord = s . nextLine ( ) ; if ( set . contains ( currWord ) ) { isValid = false ; } set . add ( currWord ) ; if ( isValid && i != 0 ) { if ( prevWord . charAt ( prevWord . length ( ) - 1 ) != currWord . charAt ( 0 ) ) { isValid = false ; } } prevWord = currWord ; } System . out . println ( isValid ? " Yes " : " No " ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (type_identifier) name: (identifier) dimensions: (dimensions))) 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 (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (null_literal))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (null_literal))) (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)) arguments: (argument_list)))) (local_variable_declaration type: (boolean_type) declarator: (variable_declarator name: (identifier) value: (true))) (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 (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (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))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) consequence: (block (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal)))) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (decimal_integer_literal))))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (false))))))) (expression_statement (assignment_expression left: (identifier) right: (identifier))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (ternary_expression condition: (identifier) consequence: (string_literal) alternative: (string_literal)))))))