YES O(n^2) TRS: { 0() -> n__0(), f(X) -> n__f(X), f(0()) -> cons(0(), n__f(n__s(n__0()))), f(s(0())) -> f(p(s(0()))), p(s(0())) -> 0(), s(X) -> n__s(X), activate(X) -> X, activate(n__f(X)) -> f(activate(X)), activate(n__s(X)) -> s(activate(X)), activate(n__0()) -> 0() } DUP: We consider a non-duplicating system. Trs: { 0() -> n__0(), f(X) -> n__f(X), f(0()) -> cons(0(), n__f(n__s(n__0()))), f(s(0())) -> f(p(s(0()))), p(s(0())) -> 0(), s(X) -> n__s(X), activate(X) -> X, activate(n__f(X)) -> f(activate(X)), activate(n__s(X)) -> s(activate(X)), activate(n__0()) -> 0() } Matrix Interpretation: Interpretation class: triangular [X1] [1 3][X1] [2] [activate]([X0]) = [0 1][X0] + [3] [X1] [1 0][X1] [1] [s]([X0]) = [0 1][X0] + [1] [X1] [1 0][X1] [0] [p]([X0]) = [0 0][X0] + [1] [X1] [1 1][X1] [1] [f]([X0]) = [0 1][X0] + [2] [0] [n__0] = [0] [X1] [1 0][X1] [0] [n__s]([X0]) = [0 1][X0] + [1] [X1] [1 1][X1] [0] [n__f]([X0]) = [0 1][X0] + [2] [1] [0] = [1] [X3] [X1] [1 0][X3] [1 0][X1] [0] [cons]([X2], [X0]) = [0 0][X2] + [0 0][X0] + [0] Qed