4 - (5/6)^(4/5)^(3/4)^(2/3)^(0.5)^(4/5)^(3/4)^(2/3)^(3/4)^(8/9)^(9)^(8/9)^(2/3)^(3/4)^(4/5)^(8)^(1/2)