Shifting (compression) FC2n for1≤i<j≤m VTEF,write Tij=(T)Uti (i,)-shift::S（) T∈F, -任 ifj∈T,i年T,and Tij年F, otherwise. S(F)={S(T)|T∈F}Shifting (compression) Sij (T) = ￾ Tij if j ￾ T,i ⇥￾ T, and Tij ⇥￾ F, T otherwise. F ￾ 2[n] for 1 ￾ i<j ￾ n ⇥T ￾ F, write Tij = (T \ {j}) ⌅ {i} (i, j)-shift: Sij (·) ⇥T ￾ F, Sij (F) = {Sij (T) | T ￾ F}