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