1-1/2=1/2 1-1/2-1/4=1/4 1-1/2-1/4-1/8=1/8 1-1/2-1/4-1/8-1/16=1/16 .1-1/2-1/4-1/8-1/16-1/32-1/64-1/128-1/256=1/256