2-3-tree operations.

Write a program that takes a number from the command line and builds a
2-3-tree of that many random numbers. Don't use the red-black implementation
trick.

To make it easy on yourself make sure that if the number of numbers is
small, the numbers themselves are also small (e.g. only 100 numbers, make
them all two digit numbers), that way results will be easier to verify
and there will be some repeats so you'll test that everything works for
that special case. More numbers requires bigger numbers otherwise there
will be so many repeats you won't be able to tell what is happening.

After building the tree, enter an interactive loop. The user enters a
number and if it is positive the program responds with whether or not
that number appears in the tree. If the number is negative, then its
absolute value is deleted from the tree.

As always, convincing test runs are needed.