public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  String s = sc . next ( ) ;
  int a = 0 , len = s . length ( ) ;
  for ( int i = 0 ;
  i < len ;
  i ++ ) {
    char c = s . charAt ( i ) ;
    if ( c == 'a' ) a ++ ;
  }
  if ( a > len / 2 ) System . out . println ( len ) ;
  else {
    System . out . println ( ( 2 * a ) - 1 ) ;
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; String s = sc . next ( ) ; int a = 0 , len = s . length ( ) ; for ( int i = 0 ; i < len ; i ++ ) { char c = s . charAt ( i ) ; if ( c == ' a ' ) a ++ ; } if ( a > len / 2 ) System . out . println ( len ) ; else { System . out . println ( ( 2 * a ) - 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: (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)) 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 (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (character_literal))) consequence: (expression_statement (update_expression (identifier)))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) consequence: (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) 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: (decimal_integer_literal) right: (identifier))) right: (decimal_integer_literal)))))))))