good_reason(X, _) :- snow_day(X).
good_reason(X, Person) :- payday(X, Person).
good_reason(X, Person) :- X = friday, \+ works_on(saturday, Person).
good_reason(X, Person) :- X = friday, \+ has_job(Person).

good_day(X, Y) :-
	good_reason(X, Y),
	person(Y).

payday(X, Person) :- last_day(X), has_job(Person).

snow_day(X) :- icy(X).
snow_day(X) :- snowy(X).