public static void main ( String [ ] args ) throws IOException {
  BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  String str = br . readLine ( ) ;
  int [ ] rb = {
    0 , 0 };
    for ( String s : str . split ( "" ) ) {
      if ( s . equals ( "0" ) ) {
        rb [ 0 ] ++ ;
      }
      else {
        rb [ 1 ] ++ ;
      }
    }
    System . out . println ( Math . min ( rb [ 0 ] , rb [ 1 ] ) * 2 ) ;
  }
  
public static void main ( String [ ] args ) throws IOException { BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ; String str = br . readLine ( ) ; int [ ] rb = { 0 , 0 } ; for ( String s : str . split ( " " ) ) { if ( s . equals ( "0" ) ) { rb [ 0 ] ++ ; } else { rb [ 1 ] ++ ; } } System . out . println ( Math . min ( rb [ 0 ] , rb [ 1 ] ) * 2 ) ; }
(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 (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))))) (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: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_initializer (decimal_integer_literal) (decimal_integer_literal)))) (enhanced_for_statement type: (type_identifier) name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (string_literal))) body: (block (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (string_literal)))) consequence: (block (expression_statement (update_expression (array_access array: (identifier) index: (decimal_integer_literal))))) alternative: (block (expression_statement (update_expression (array_access array: (identifier) index: (decimal_integer_literal)))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (decimal_integer_literal)) (array_access array: (identifier) index: (decimal_integer_literal)))) right: (decimal_integer_literal)))))))