MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { minus(0(), x) -> 0() , minus(s(x), 0()) -> s(x) , minus(s(x), s(y)) -> minus(x, y) , mod(x, 0()) -> 0() , mod(x, s(y)) -> if(lt(x, s(y)), x, s(y)) , if(true(), x, y) -> x , if(false(), x, y) -> mod(minus(x, y), y) , lt(x, 0()) -> false() , lt(0(), s(x)) -> true() , lt(s(x), s(y)) -> lt(x, y) , gcd(x, 0()) -> x , gcd(0(), s(y)) -> s(y) , gcd(s(x), s(y)) -> gcd(mod(s(x), s(y)), mod(s(y), s(x))) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..