az7 + z7a−1 + a2z6 + z6a−2 + 2z6−5az5−5z5a−1−5a2z4−5z4a−2−10z4 + 6az3 + 6z3a−1 + 6a2z2 + 6z2a−2 + 12z2−2az−2za−1−2a2−2a−2−3