Input TRS:
    1: active(f(X)) -> mark(if(X,c(),f(true())))
    2: active(if(true(),X,Y)) -> mark(X)
    3: active(if(false(),X,Y)) -> mark(Y)
    4: mark(f(X)) -> active(f(mark(X)))
    5: mark(if(X1,X2,X3)) -> active(if(mark(X1),mark(X2),X3))
    6: mark(c()) -> active(c())
    7: mark(true()) -> active(true())
    8: mark(false()) -> active(false())
    9: f(mark(X)) -> f(X)
    10: f(active(X)) -> f(X)
    11: if(mark(X1),X2,X3) -> if(X1,X2,X3)
    12: if(X1,mark(X2),X3) -> if(X1,X2,X3)
    13: if(X1,X2,mark(X3)) -> if(X1,X2,X3)
    14: if(active(X1),X2,X3) -> if(X1,X2,X3)
    15: if(X1,active(X2),X3) -> if(X1,X2,X3)
    16: if(X1,X2,active(X3)) -> if(X1,X2,X3)
Number of Rules: 16
Direct POLO(mSum) ... failed.