public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) ;
  sc . nextLine ( ) ;
  char [ ] [ ] arr = new char [ n ] [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    String temp = sc . nextLine ( ) ;
    for ( int j = 0 ;
    j < n ;
    j ++ ) {
      arr [ i ] [ j ] = temp . charAt ( j ) ;
    }
  }
  boolean flag = true ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int count = 0 ;
    for ( int j = 0 ;
    j < n ;
    j ++ ) {
      count = 0 ;
      if ( i - 1 >= 0 && arr [ ( i - 1 ) ] [ j ] == 'o' ) {
        count ++ ;
      }
      if ( i + 1 < n && arr [ i + 1 ] [ j ] == 'o' ) {
        count ++ ;
      }
      if ( j + 1 < n && arr [ i ] [ j + 1 ] == 'o' ) {
        count ++ ;
      }
      if ( j - 1 >= 0 && arr [ i ] [ j - 1 ] == 'o' ) {
        count ++ ;
      }
      if ( count % 2 != 0 ) {
        flag = false ;
        break ;
      }
    }
  }
  if ( flag ) {
    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 ( ) ; sc . nextLine ( ) ; char [ ] [ ] arr = new char [ n ] [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { String temp = sc . nextLine ( ) ; for ( int j = 0 ; j < n ; j ++ ) { arr [ i ] [ j ] = temp . charAt ( j ) ; } } boolean flag = true ; for ( int i = 0 ; i < n ; i ++ ) { int count = 0 ; for ( int j = 0 ; j < n ; j ++ ) { count = 0 ; if ( i - 1 >= 0 && arr [ ( i - 1 ) ] [ j ] == ' o ' ) { count ++ ; } if ( i + 1 < n && arr [ i + 1 ] [ j ] == ' o ' ) { count ++ ; } if ( j + 1 < n && arr [ i ] [ j + 1 ] == ' o ' ) { count ++ ; } if ( j - 1 >= 0 && arr [ i ] [ j - 1 ] == ' o ' ) { count ++ ; } if ( count % 2 != 0 ) { flag = false ; break ; } } } if ( flag ) { 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)))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier)) dimensions: (dimensions_expr (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 (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (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: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))))))) (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 (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_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 (expression_statement (assignment_expression left: (identifier) right: (decimal_integer_literal))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal)) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal)))) index: (identifier)) right: (character_literal)))) consequence: (block (expression_statement (update_expression (identifier))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (identifier)) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) index: (identifier)) right: (character_literal)))) consequence: (block (expression_statement (update_expression (identifier))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (identifier)) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (character_literal)))) consequence: (block (expression_statement (update_expression (identifier))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal)) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (character_literal)))) consequence: (block (expression_statement (update_expression (identifier))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (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))))))))