Input TRS:
    1: f(x,a(b(y))) -> f(a(b(x)),y)
    2: f(x,b(c(y))) -> f(b(c(x)),y)
    3: f(x,c(a(y))) -> f(c(a(x)),y)
    4: f(a(x),y) -> f(x,a(y))
    5: f(b(x),y) -> f(x,b(y))
    6: f(c(x),y) -> f(x,c(y))
Number of Rules: 6
Direct POLO(Sum) ... failed.