Original	De Morgan
!(x > 0 && y > 0)	(x <= 0 || y <= 0)
!(x != 0 || y != 0)	(x == 0 && y == 0)
! (country == "USA" && state != "HI" && state != "AK")	(country != "USA" || state == "HI" || state == "AK")
!(x % 4 != 0 || !(x % 100 == 0 && x % 400 != 0))	(x % 4 == 0 && x % 100 == 0 && x % 400 != 0)