YES(?,O(1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(1)). Strict Trs: { b(x, y) -> c(a(c(y), a(0(), x))) , a(y, x) -> y , a(y, c(b(a(0(), x), 0()))) -> b(a(c(b(0(), y)), x), 0()) } Obligation: innermost runtime complexity Answer: YES(?,O(1)) Arguments of following rules are not normal-forms: { a(y, c(b(a(0(), x), 0()))) -> b(a(c(b(0(), y)), x), 0()) } All above mentioned rules can be savely removed. We are left with following problem, upon which TcT provides the certificate YES(?,O(1)). Strict Trs: { b(x, y) -> c(a(c(y), a(0(), x))) , a(y, x) -> y } Obligation: innermost runtime complexity Answer: YES(?,O(1)) The input was oriented with the instance of 'Small Polynomial Path Order (PS,0-bounded)' as induced by the safe mapping safe(b) = {1}, safe(c) = {1}, safe(a) = {1, 2}, safe(0) = {} and precedence b > a . Following symbols are considered recursive: {} The recursion depth is 0. For your convenience, here are the satisfied ordering constraints: b(y; x) > c(; a(; c(; y), a(; 0(), x))) a(; y, x) > y Hurray, we answered YES(?,O(1))