We consider termination of the STRS with no additional rule schemes: Signature: 0 :: nat 1 :: nat f :: nat -> (nat -> nat) -> nat Rules: f(0, F) -> F(f(F(1), F)) The system is accessible function passing by a sort ordering that equates all sorts. We start by computing the initial DP problem D1 = (P1, R, i, c), where: P1. (1) f#(0, F) => f#(F(1), F) ***** No progress could be made on DP problem D1 = (P1, R, i, c).