Input TRS:
    1: active(f(X)) -> mark(g(h(f(X))))
    2: mark(f(X)) -> active(f(mark(X)))
    3: mark(g(X)) -> active(g(X))
    4: mark(h(X)) -> active(h(mark(X)))
    5: f(mark(X)) -> f(X)
    6: f(active(X)) -> f(X)
    7: g(mark(X)) -> g(X)
    8: g(active(X)) -> g(X)
    9: h(mark(X)) -> h(X)
    10: h(active(X)) -> h(X)
Number of Rules: 10
Direct QKBOS(Sum) ... failed.