1/4 a^{v0}_{c2} b^{c0,c1}_{c3,a0} c^{c2,c3}_{a1,a2} a+(a0) a+(a1) a+(a2) a-(v0) a-(c1) a-(c0)
-1/2 a^{v0}_{c2} b^{c0,c2}_{c3,a0} c^{c1,c3}_{a1,a2} a+(a0) a+(a1) a+(a2) a-(v0) a-(c1) a-(c0)