YES O(n^5) TRS: {f(f(x)) -> f(x), f(1()) -> f(g(1())), g(g(x)) -> g(x), g(0()) -> g(f(0()))} DUP: We consider a non-duplicating system. Trs: {f(f(x)) -> f(x), f(1()) -> f(g(1())), g(g(x)) -> g(x), g(0()) -> g(f(0())) } Matrix Interpretation: Interpretation class: triangular [0] [0] [0] = [0] [0] [1] [0] [1] [1] = [1] [1] [0] [X4] [1 0 0 0 1][X4] [0] [X3] [0 0 0 0 0][X3] [0] [g]([X2]) = [0 0 0 0 0][X2] + [0] [X1] [0 0 0 0 0][X1] [0] [X0] [0 0 0 0 0][X0] [1] [X4] [1 0 1 1 0][X4] [0] [X3] [0 1 0 1 0][X3] [0] [f]([X2]) = [0 0 0 0 0][X2] + [1] [X1] [0 0 0 0 0][X1] [0] [X0] [0 0 0 0 0][X0] [0] Qed