(VAR X Y Z X1 X2) (RULES a__2nd(cons1(X,cons(Y,Z))) -> mark(Y) a__2nd(cons(X,X1)) -> a__2nd(cons1(mark(X),mark(X1))) a__from(X) -> cons(mark(X),from(s(X))) mark(2nd(X)) -> a__2nd(mark(X)) mark(from(X)) -> a__from(mark(X)) mark(cons(X1,X2)) -> cons(mark(X1),X2) mark(s(X)) -> s(mark(X)) mark(cons1(X1,X2)) -> cons1(mark(X1),mark(X2)) a__2nd(X) -> 2nd(X) a__from(X) -> from(X) )