Obstacle problem in 2D and its aposteriori error estimate

An obstacle problem is solved and the error of the solution is estimated

This code demonstrates concepts from the paper
Petr Harasim, Jan Valdman, Verification of functional a posteriori error estimates for an obstacle problem in 2D, Kybernetika 50, No. 6, 978-1002 (2014)

A link to the paper can be found at the author web page located at http://sites.google.com/site/janvaldman/publications

Please cite the paper when you find the code useful.

Description; Type "start" to solve a 2D obstacle problem.