YES O(n^4) TRS: { mark(g(X)) -> active(g(X)), mark(h(X)) -> active(h(mark(X))), mark(f(X)) -> active(f(mark(X))), g(mark(X)) -> g(X), g(active(X)) -> g(X), h(mark(X)) -> h(X), h(active(X)) -> h(X), f(mark(X)) -> f(X), f(active(X)) -> f(X), active(f(X)) -> mark(g(h(f(X)))) } DUP: We consider a non-duplicating system. Trs: { mark(g(X)) -> active(g(X)), mark(h(X)) -> active(h(mark(X))), mark(f(X)) -> active(f(mark(X))), g(mark(X)) -> g(X), g(active(X)) -> g(X), h(mark(X)) -> h(X), h(active(X)) -> h(X), f(mark(X)) -> f(X), f(active(X)) -> f(X), active(f(X)) -> mark(g(h(f(X)))) } Matrix Interpretation: Interpretation class: triangular [X3] [1 2 0 0][X3] [1] [X2] [0 0 0 0][X2] [0] [active]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 1][X0] [0] [X3] [1 0 0 0][X3] [3] [X2] [0 0 0 0][X2] [2] [f]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 1][X0] [3] [X3] [1 0 0 0][X3] [0] [X2] [0 0 0 0][X2] [0] [h]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 1][X0] [1] [X3] [1 0 0 0][X3] [0] [X2] [0 0 0 0][X2] [0] [g]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 0][X0] [1] [X3] [1 0 0 2][X3] [1] [X2] [0 0 0 0][X2] [0] [mark]([X1]) = [0 0 0 0][X1] + [0] [X0] [0 0 0 1][X0] [0] Qed