YES O(n^3) TRS: { .(x, 1()) -> x, .(x, i(x)) -> 1(), .(y, .(i(y), z)) -> z, .(1(), x) -> x, .(i(x), x) -> 1(), .(i(y), .(y, z)) -> z, i(1()) -> 1(), i(i(x)) -> x } DUP: We consider a non-duplicating system. Trs: { .(x, 1()) -> x, .(x, i(x)) -> 1(), .(y, .(i(y), z)) -> z, .(1(), x) -> x, .(i(x), x) -> 1(), .(i(y), .(y, z)) -> z, i(1()) -> 1(), i(i(x)) -> x } Matrix Interpretation: Interpretation class: triangular [X2] [1 1 0][X2] [0] [i]([X1]) = [0 1 0][X1] + [1] [X0] [0 0 1][X0] [0] [0] [1] = [1] [0] [X5] [X2] [1 0 0][X5] [1 0 0][X2] [1] [.]([X4], [X1]) = [0 1 0][X4] + [0 1 0][X1] + [0] [X3] [X0] [0 0 1][X3] [0 0 1][X0] [0] Qed