The boys propose (to their top-ranked girl that hasn't yet rejected them) and the girls tentatively accept. This is an engagement.
If a girl ever gets an offer from a boy that she likes better than her current fiance, she breaks her old engagement for him.
Stop when all boys are engaged.
M holds the tentative matching. records the
rank position of b's most recent rejection (ouch).
Once b is rejected by g, b never needs to propose to g again. Why?
(It is possible to also have the girls do the proposing... we will return to this later.)
Example!