public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int n = in . nextInt ( ) , k = in . nextInt ( ) ;
  ArrayList < Integer > f = new ArrayList < Integer > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) f . add ( in . nextInt ( ) ) ;
  Collections . sort ( f , Collections . reverseOrder ( ) ) ;
  int c = 0 ;
  for ( int i = 0 ;
  i < n ;
  i += k ) c += f . get ( i ) - 1 ;
  System . out . println ( 2 * c ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int n = in . nextInt ( ) , k = in . nextInt ( ) ; ArrayList < Integer > f = new ArrayList < Integer > ( ) ; for ( int i = 0 ; i < n ; i ++ ) f . add ( in . nextInt ( ) ) ; Collections . sort ( f , Collections . reverseOrder ( ) ) ; int c = 0 ; for ( int i = 0 ; i < n ; i += k ) c += f . get ( i ) - 1 ; System . out . println ( 2 * c ) ; }
(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: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) 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 (type_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: (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (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: (assignment_expression left: (identifier) right: (identifier)) body: (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (decimal_integer_literal))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (decimal_integer_literal) right: (identifier)))))))