YES O(n^4) TRS: { \(x, x) -> e(), \(x, .(x, y)) -> y, \(e(), x) -> x, \(/(x, y), x) -> y, /(x, x) -> e(), /(x, e()) -> x, /(x, \(y, x)) -> y, /(.(y, x), x) -> y, .(x, e()) -> x, .(x, \(x, y)) -> y, .(e(), x) -> x, .(/(y, x), x) -> y } DUP: We consider a non-duplicating system. Trs: { \(x, x) -> e(), \(x, .(x, y)) -> y, \(e(), x) -> x, \(/(x, y), x) -> y, /(x, x) -> e(), /(x, e()) -> x, /(x, \(y, x)) -> y, /(.(y, x), x) -> y, .(x, e()) -> x, .(x, \(x, y)) -> y, .(e(), x) -> x, .(/(y, x), x) -> y } Matrix Interpretation: Interpretation class: triangular [X7] [X3] [1 0 0 0][X7] [1 0 0 0][X3] [1] [X6] [X2] [0 1 0 0][X6] [0 1 0 0][X2] [0] [.]([X5], [X1]) = [0 0 1 0][X5] + [0 0 1 0][X1] + [0] [X4] [X0] [0 0 0 1][X4] [0 0 0 1][X0] [0] [X7] [X3] [1 0 0 0][X7] [1 0 0 0][X3] [1] [X6] [X2] [0 1 0 0][X6] [0 1 0 0][X2] [0] [/]([X5], [X1]) = [0 0 1 0][X5] + [0 0 1 0][X1] + [0] [X4] [X0] [0 0 0 1][X4] [0 0 0 1][X0] [1] [X7] [X3] [1 0 0 1][X7] [1 0 0 0][X3] [1] [X6] [X2] [0 1 0 0][X6] [0 1 0 0][X2] [0] [\]([X5], [X1]) = [0 0 1 0][X5] + [0 0 1 0][X1] + [0] [X4] [X0] [0 0 0 1][X4] [0 0 0 1][X0] [0] [0] [0] [e] = [0] [0] Qed