MICheckList {
(@
public void add(Vertex a, Vertex b) {
if (a.equals(b)) return;
if (next!=null)
	{this.next.add(a,b); return;}
sub=a;
superc=b;
next=new MICheckList();
}

public MICheckList contains(Vertex a) {
if (next!=null)
{if (sub.equals(a)) {
return this;
}
else return this.next.contains(a);}
return null;
}
@)
}