(VAR YS X XS Y L)

(RULES 
app(nil,YS) -> YS
app(cons(X,XS),YS) -> cons(X,app(XS,YS))
from(X) -> cons(X,from(s(X)))
zWadr(nil,YS) -> nil
zWadr(XS,nil) -> nil
zWadr(cons(X,XS),cons(Y,YS)) -> cons(app(Y,cons(X,nil)),zWadr(XS,YS))
prefix(L) -> cons(nil,zWadr(L,prefix(L)))
)