n1:=7340;n2:=2060;n3:=1;n4:=1; B:=(C*N1+O*N2+H*N3+L*N4)/(N1+N2+N3+N4); D:=((((H-L)/2)+L)+((ABS(O-C)/2)+L))/2; e:=ref(d,1); 进:cross(d,e); 退:cross(e,d);
