YES O(n^2) TRS: {f(s(s(x))) -> f(f(s(x))), f(s(0())) -> s(0()), f(0()) -> s(0())} DUP: We consider a non-duplicating system. Trs: {f(s(s(x))) -> f(f(s(x))), f(s(0())) -> s(0()), f(0()) -> s(0())} Matrix Interpretation: Interpretation class: triangular [X1] [1 0][X1] [1] [f]([X0]) = [0 0][X0] + [2] [0] [0] = [0] [X1] [1 1][X1] [0] [s]([X0]) = [0 0][X0] + [2] Qed