i can show u algorithm :
WriteIf(F1:=ValueWhen(1,H<Ref(H,-2) AND Ref(H,-1)<Ref(H,-2) AND Ref(H,-3)<Ref(H,-2) AND Ref(H,-4)<Ref(H,-2),Ref(H,-2));F2:=ValueWhen(1,L>Ref(L,-2) AND Ref(L,-1)>Ref(L,-2) AND Ref(L,-3)>Ref(L,-2) AND Ref(L,-4)>Ref(L,-2),Ref(L,-2));a:=Cross(H,F1);b:=Cross(F2,L)...