eBGDAElet ringlet ring1=8002002(0)24302(0)442350003020let ringlet ring302002(0)24302(0)43505100200let ring502002(0)21201(0)620002(0)42002let ring730005403830300(0)3020let ring902002102110200242002let ringP. M.1132020220012023204222222221355377514220220