MAYBE
0.18/0.21	MAYBE
0.18/0.21	
0.18/0.21	Problem:
0.18/0.21	 active(dbl(0())) -> mark(0())
0.18/0.21	 active(dbl(s(X))) -> mark(s(s(dbl(X))))
0.18/0.21	 active(dbls(nil())) -> mark(nil())
0.18/0.21	 active(dbls(cons(X,Y))) -> mark(cons(dbl(X),dbls(Y)))
0.18/0.21	 active(sel(0(),cons(X,Y))) -> mark(X)
0.18/0.21	 active(sel(s(X),cons(Y,Z))) -> mark(sel(X,Z))
0.18/0.21	 active(indx(nil(),X)) -> mark(nil())
0.18/0.21	 active(indx(cons(X,Y),Z)) -> mark(cons(sel(X,Z),indx(Y,Z)))
0.18/0.21	 active(from(X)) -> mark(cons(X,from(s(X))))
0.18/0.21	 active(dbl(X)) -> dbl(active(X))
0.18/0.21	 active(dbls(X)) -> dbls(active(X))
0.18/0.21	 active(sel(X1,X2)) -> sel(active(X1),X2)
0.18/0.21	 active(sel(X1,X2)) -> sel(X1,active(X2))
0.18/0.21	 active(indx(X1,X2)) -> indx(active(X1),X2)
0.18/0.21	 dbl(mark(X)) -> mark(dbl(X))
0.18/0.21	 dbls(mark(X)) -> mark(dbls(X))
0.18/0.21	 sel(mark(X1),X2) -> mark(sel(X1,X2))
0.18/0.21	 sel(X1,mark(X2)) -> mark(sel(X1,X2))
0.18/0.21	 indx(mark(X1),X2) -> mark(indx(X1,X2))
0.18/0.21	 proper(dbl(X)) -> dbl(proper(X))
0.18/0.21	 proper(0()) -> ok(0())
0.18/0.21	 proper(s(X)) -> s(proper(X))
0.18/0.21	 proper(dbls(X)) -> dbls(proper(X))
0.18/0.21	 proper(nil()) -> ok(nil())
0.18/0.21	 proper(cons(X1,X2)) -> cons(proper(X1),proper(X2))
0.18/0.21	 proper(sel(X1,X2)) -> sel(proper(X1),proper(X2))
0.18/0.21	 proper(indx(X1,X2)) -> indx(proper(X1),proper(X2))
0.18/0.21	 proper(from(X)) -> from(proper(X))
0.18/0.21	 dbl(ok(X)) -> ok(dbl(X))
0.18/0.21	 s(ok(X)) -> ok(s(X))
0.18/0.21	 dbls(ok(X)) -> ok(dbls(X))
0.18/0.21	 cons(ok(X1),ok(X2)) -> ok(cons(X1,X2))
0.18/0.21	 sel(ok(X1),ok(X2)) -> ok(sel(X1,X2))
0.18/0.21	 indx(ok(X1),ok(X2)) -> ok(indx(X1,X2))
0.18/0.21	 from(ok(X)) -> ok(from(X))
0.18/0.21	 top(mark(X)) -> top(proper(X))
0.18/0.21	 top(ok(X)) -> top(active(X))
0.18/0.21	
0.18/0.21	Proof:
0.18/0.21	 Open
0.18/0.21	EOF