W(e)=ΣV(e)^n
W0=V(e)^0={e}
v∈V(e)∩aW
v=aw
f(v)=e=af(w)
f(w)=c
w∈W(c)=W(e)cW(e)
v∈V(e)∩aW(e)cW(e)
v∈aW(e)c
V[c]=V(e)∩aW(e)c
V(e)=V[a]+V[b]+V[c]+V[d]
v∈V[c]=V(e)∩aΣV(e)^nc
v=av1…vnc
うーん