1------------------>2
         >   <               > | <
       /       .           /   |   .
     /           .       /     |     .
   /               .   /       |       .
 6                   .         |         3
   <               /   .       |       >
     .           /       .     |     /
       .       /           .   |   /
         .   /               . v /
           5<------------------4
            ------------------>

\fBDirected Graph.\fP