YES linear polynomial interpretations on natural numbers: g_A(x1,x2) = x2 h_A(x1) = x1 f_A(x1,x2) = x2 a_A = 1 b_A = 0 F_A(x1,x2) = x2 the condition F(x,g(x,b())) ->> F(y,a()) is unsatisfiable for all substitutions.