Construct the Delaunay triangulation and Voronoi diagram of the given
point set.

In this exercise you do not need to simulate any
algorithm, only to produce the correct solution.

You can modify the given TIN by mouse. By clicking on two points,
an edge will be added between them. Edges can also be modified by
clicking. If the clicked edge is diagonal of a given quadrilateral,
clicking the edge will replace it with the other diagonal of the same
quadrilateral. If the edge is not a diagonal, then clicking it will remove
the edge.

By clicking on a triangle, the circumscribing circle of the triangle
is shown. Valid triangles are highlighted when mouse is moved over
them.