method f1(a b)
	return not(a or b);
end;

method f2(a b)
	return not(not(a or b));
end;

method f3(a b)
	return not(a - b);
end;

method f4(a b)
	return not(not(a - b));
end;

method f5(a b)
	return not(a < b);
end;

method f6(a b)
	return not(not(a < b));
end;

method f7(a b)
	return not(a = b);
end;

method f8(a b)
	return not(not(a = b));
end;