suml(p(v,0))=s(0), suml(p(v,s(0)))=0, suml(p(v,s(s(0))))=s(0), suml(p(p(v,0),s(0)))=s(s(0)), suml(p(p(v,s(0)),s(0)))=s(s(s(0))), suml(p(p(v,s(0)),s(0)))=s(0), suml(p(p(v,s(0)),s(s(0))))=s(s(0)), suml(p(p(v,0),s(s(0))))=s(s(s(0))), suml(p(p(p(v,s(0)),s(0)),s(0)))=s(s(0)), suml(p(p(p(v,s(0)),0),s(0)))=s(0)