1/2 a^{v0,v1}_{c0,a0} b^{a1,v2}_{c1,c3} c^{c3}_{c2} gamma1^{a0}_{a1} a+(c0) a+(c1) a+(c2) a-(v2) a-(v1) a-(v0)
+1/4 a^{v0,v1}_{c3,a0} b^{a1,v2}_{c0,c1} c^{c3}_{c2} gamma1^{a0}_{a1} a+(c0) a+(c1) a+(c2) a-(v2) a-(v1) a-(v0)