public static void main ( String [ ] args ) {
  Scanner scanner = new Scanner ( System . in ) ;
  String line = scanner . nextLine ( ) ;
  Stack < Character > items = new Stack < > ( ) ;
  for ( char letter : line . toCharArray ( ) ) {
    if ( Character . isDigit ( letter ) ) {
      items . push ( letter ) ;
    }
    else if ( letter == 'B' && ! items . isEmpty ( ) ) {
      items . pop ( ) ;
    }
  }
  StringBuilder builder = new StringBuilder ( ) ;
  for ( char letter : items ) {
    builder . append ( letter ) ;
  }
  System . out . println ( builder ) ;
}

public static void main ( String [ ] args ) { Scanner scanner = new Scanner ( System . in ) ; String line = scanner . nextLine ( ) ; Stack < Character > items = new Stack < > ( ) ; for ( char letter : line . toCharArray ( ) ) { if ( Character . isDigit ( letter ) ) { items . push ( letter ) ; } else if ( letter == ' B ' && ! items . isEmpty ( ) ) { items . pop ( ) ; } } StringBuilder builder = new StringBuilder ( ) ; for ( char letter : items ) { builder . append ( letter ) ; } System . out . println ( builder ) ; }
(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: (generic_type (type_identifier) (type_arguments (type_identifier))) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (generic_type (type_identifier) (type_arguments)) arguments: (argument_list)))) (enhanced_for_statement type: (integral_type) name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) body: (block (if_statement condition: (parenthesized_expression (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) consequence: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))))) alternative: (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (character_literal)) right: (unary_expression operand: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))) consequence: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list)))) (enhanced_for_statement type: (integral_type) name: (identifier) value: (identifier) body: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))