let
	type counter = int
	var c : counter := 0

	function knockKnock() =
	(
		if c = 0 then
			print("Knock knock.\n")
		else if c = 1 then
			print("Who's there?\n")
		else if c = 2 then 
			print("Little old lady.\n")
		else if c = 3 then
			print("Little old lady who?\n")
		else
			print("I didn't know you could yodel!\n");
		c := c + 1;
		if c > 4 then c := 0
	)

in
	knockKnock();
	knockKnock();
	knockKnock();
	knockKnock();
	knockKnock()
end