MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { U11(tt(), N, X, XS) -> U12(splitAt(N, XS), X) , U12(pair(YS, ZS), X) -> pair(cons(X, YS), ZS) , splitAt(s(N), cons(X, XS)) -> U11(tt(), N, X, XS) , splitAt(0(), XS) -> pair(nil(), XS) , afterNth(N, XS) -> snd(splitAt(N, XS)) , snd(pair(X, Y)) -> Y , and(tt(), X) -> X , fst(pair(X, Y)) -> X , head(cons(N, XS)) -> N , natsFrom(N) -> cons(N, natsFrom(s(N))) , sel(N, XS) -> head(afterNth(N, XS)) , tail(cons(N, XS)) -> XS , take(N, XS) -> fst(splitAt(N, XS)) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..