ZL:='ZL000001';
   vEndt:=today();
   PZ:=spec(base(703003),ZLToFuturesID(ZL,vEndt));
   stocks:= GetFuturesID(PZ,vEndt);
   setsysparam(pn_date(),vEndt);
   ccD:=select thisrow as 'id',spec(SectionOpenInterest(),thisrow) as 'ccl'
   from stocks end;
   ccD:=select * from ccD order by ['ccl'] desc end;
if ccD[0,'ccl']=0 then return ZLToFuturesID(ZL,vEndt-1);
   else return ccD[0,'id'];