四个二分之一填符号1/21/21/21/2=01/21/21/21/2=11/21/21/21/2=21/21/21/21/2=31/21/21/21/2=4

　　四个二分之一填符号

　　1/21/21/21/2=0

　　1/21/21/21/2=1

　　1/21/21/21/2=2

　　1/21/21/21/2=3

　　1/21/21/21/2=4