public static void main ( String [ ] args ) {
  Scanner scanner = new Scanner ( System . in ) ;
  int n = scanner . nextInt ( ) ;
  if ( n % 2 == 1 ) System . out . println ( - 1 ) ;
  else for ( int i = 1 ;
  i <= n ;
  i ++ ) {
    if ( i % 2 == 1 ) {
      System . out . print ( ( i + 1 ) + " " ) ;
    }
    else {
      System . out . print ( ( i - 1 ) + " " ) ;
    }
  }
}

public static void main ( String [ ] args ) { Scanner scanner = new Scanner ( System . in ) ; int n = scanner . nextInt ( ) ; if ( n % 2 == 1 ) System . out . println ( - 1 ) ; else for ( int i = 1 ; i <= n ; i ++ ) { if ( i % 2 == 1 ) { System . out . print ( ( i + 1 ) + " ▁ " ) ; } else { System . out . print ( ( i - 1 ) + " ▁ " ) ; } } }
(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)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (unary_expression operand: (decimal_integer_literal))))) alternative: (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 (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (string_literal)))))) alternative: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (string_literal))))))))))))