−za13 + a13z−3 + z5a11 + 4z3a11 + za11−5a11z−1−3a11z−3−z7a9−4z5a9 + 11za9 + 10a9z−1 + 3a9z−3−z7a7−6z5a7−12z3a7−11za7−5a7z−1−a7z−3