WP 34S mini-challenge

[Gerson W. Barbosa]

Consider the following HP-15C program:



(this listing courtesy of Torsten's HP-15C Simulator)

It computes the sum of the first n natural numbers using Gauss's formula. For instance,

100000 GSB A --> 5000050000

Write an equivalent WP 34S program using the same number of steps at most (5, if we don't count LBL and RTN) and preserving the stack (that is, Y, Z and T registers must not be affected by the program). The default settings must be kept unchanged at program termination.