YES(?,O(n^2)) Problem: f(f(x)) -> f(x) f(s(x)) -> f(x) g(s(0())) -> g(f(s(0()))) Proof: Matrix Interpretation Processor: dimension: 2 interpretation: [1 6] [1] [g](x0) = [0 0]x0 + [0], [8] [0] = [0], [1 4] [4] [s](x0) = [0 0]x0 + [1], [1 0] [5] [f](x0) = [0 0]x0 + [0] orientation: [1 0] [10] [1 0] [5] f(f(x)) = [0 0]x + [0 ] >= [0 0]x + [0] = f(x) [1 4] [9] [1 0] [5] f(s(x)) = [0 0]x + [0] >= [0 0]x + [0] = f(x) [19] [18] g(s(0())) = [0 ] >= [0 ] = g(f(s(0()))) problem: Qed