Input TRS:
    1: concat(leaf(),Y) -> Y
    2: concat(cons(U,V),Y) -> cons(U,concat(V,Y))
    3: lessleaves(X,leaf()) -> false()
    4: lessleaves(leaf(),cons(W,Z)) -> true()
    5: lessleaves(cons(U,V),cons(W,Z)) -> lessleaves(concat(U,V),concat(W,Z))
Number of Rules: 5
Direct POLO(mSum) ... failed.