-- There is PVW, which is easier and better, if you
are clever enough to think of it; and
-- There is a third method which is even more clever
and more elegant.
=====
It's really good exercise to find _more than one way_
of solving this problem.
It's hard enough to motivate students to solve a given
homework problem once, let alone more than once. But
still, it is really good exercise. Being able to see
things in more than one way is an important higher-level
thinking skill.