1∕2x1∕2x1∕2x1∕2x1∕2x1∕2x1∕2x1∕2x1∕2x1∕2x1∕2=（2的11次方分之一）=1∕2048
=0.5*0.5*0.5*0.5*0.5*0.5*0.5*0.5*0.5*0.5*0.5=0.04882%
