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