RES
1b:x-dxyl-PEN-1:5
2r:r1
3b:b-dxyl-PEN-1:5
LIN
1:1o(4+1)2n
2:2n(4+1)3d
REP
REP1:4o(4+1)4d=-1--1
RES
4b:b-dxyl-PEN-1:5