Input TRS:
    1: a(a(f(x,y))) -> f(a(b(a(b(a(x))))),a(b(a(b(a(y))))))
    2: f(a(x),a(y)) -> a(f(x,y))
    3: f(b(x),b(y)) -> b(f(x,y))
Number of Rules: 3
Direct QWPOS(Sum) ... failed.