TIMEOUT
MAYBE
Trs:
 {     active(f(x)) -> mark(f(f(x))),
       f(active(x)) -> active(f(x)),
           f(no(x)) -> no(f(x)),
         f(mark(x)) -> mark(f(x)),
     mat(f(x), c()) -> no(c()),
  mat(f(x), f(y())) -> f(mat(x, y())),
       chk(no(c())) -> active(c()),
      chk(no(f(x))) -> f(chk(mat(f(f(f(f(f(f(f(f(f(f(X())))))))))), x))),
        tp(mark(x)) -> tp(chk(mat(f(f(f(f(f(f(f(f(f(f(X())))))))))), x)))}
 Open