public static void main ( String [ ] args ) {
  int h1 = Integer . parseInt ( sc . next ( ) ) ;
  int w1 = Integer . parseInt ( sc . next ( ) ) ;
  int h2 = Integer . parseInt ( sc . next ( ) ) ;
  int w2 = Integer . parseInt ( sc . next ( ) ) ;
  int count = 0 ;
  if ( h1 == h2 && w1 == w2 ) {
    count = 0 ;
  }
  else {
    count = h1 * w1 - ( h2 * w2 + ( h2 * ( w1 - w2 ) ) + ( w2 * ( h1 - h2 ) ) ) ;
  }
  System . out . println ( count ) ;
  System . out . flush ( ) ;
  sc . close ( ) ;
}

public static void main ( String [ ] args ) { int h1 = Integer . parseInt ( sc . next ( ) ) ; int w1 = Integer . parseInt ( sc . next ( ) ) ; int h2 = Integer . parseInt ( sc . next ( ) ) ; int w2 = Integer . parseInt ( sc . next ( ) ) ; int count = 0 ; if ( h1 == h2 && w1 == w2 ) { count = 0 ; } else { count = h1 * w1 - ( h2 * w2 + ( h2 * ( w1 - w2 ) ) + ( w2 * ( h1 - h2 ) ) ) ; } System . out . println ( count ) ; System . out . flush ( ) ; sc . close ( ) ; }
(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: (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: (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: (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: (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: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (binary_expression left: (identifier) right: (identifier)))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (decimal_integer_literal)))) alternative: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (parenthesized_expression (binary_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (identifier)))))) right: (parenthesized_expression (binary_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (identifier)))))))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))