public static void main ( String [ ] args ) throws Exception {
  Scanner sc = new Scanner ( System . in ) ;
  int A = sc . nextInt ( ) ;
  int B = sc . nextInt ( ) ;
  int C = sc . nextInt ( ) ;
  Long K = sc . nextLong ( ) ;
  int ans = 0 ;
  if ( K % 2 == 1 ) {
    ans = B - A ;
  }
  else {
    ans = A - B ;
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) throws Exception { Scanner sc = new Scanner ( System . in ) ; int A = sc . nextInt ( ) ; int B = sc . nextInt ( ) ; int C = sc . nextInt ( ) ; Long K = sc . nextLong ( ) ; int ans = 0 ; if ( K % 2 == 1 ) { ans = B - A ; } else { ans = A - B ; } System . out . println ( ans ) ; }
(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 (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: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (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: (type_identifier) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (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: (binary_expression left: (identifier) right: (identifier))))) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (identifier)))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))