public static void main ( String [ ] args ) throws IOException {
  MyScanner sc = new MyScanner ( ) ;
  PrintWriter out = new PrintWriter ( System . out ) ;
  int n = sc . nextInt ( ) ;
  int k = sc . nextInt ( ) ;
  long ans = 0 , cur = 2 * n - 3 ;
  for ( int i = 0 ;
  i < k && cur > 0 ;
  i ++ ) {
    ans += cur ;
    cur -= 4 ;
  }
  out . println ( ans ) ;
  out . flush ( ) ;
}

public static void main ( String [ ] args ) throws IOException { MyScanner sc = new MyScanner ( ) ; PrintWriter out = new PrintWriter ( System . out ) ; int n = sc . nextInt ( ) ; int k = sc . nextInt ( ) ; long ans = 0 , cur = 2 * n - 3 ; for ( int i = 0 ; i < k && cur > 0 ; i ++ ) { ans += cur ; cur -= 4 ; } out . println ( ans ) ; out . flush ( ) ; }
(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)))) (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)))) (local_variable_declaration type: (integral_type) 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: (binary_expression left: (binary_expression left: (decimal_integer_literal) right: (identifier)) right: (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: (binary_expression left: (identifier) right: (identifier)) right: (binary_expression left: (identifier) right: (decimal_integer_literal))) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (identifier) right: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (decimal_integer_literal))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier)))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))