Ap＞next=s;p＞next＞prior=s;s＞prior=p;s＞next=p＞next;Bp＞next=s;s＞prior=p;p＞next＞prior=s;s＞next=p＞next;Cs＞prior=p;s＞next=p＞next;p＞next＞prior=s;p＞next=s;Ds＞prior=p;s＞next=p＞next;p＞next=s;p＞next＞prior=s;