The idea of graphs is a very old and very interesting topic for mathematicians too. See http://en.wikipedia.org/wiki/Seven_Bridges_of_K%C3%B6nigsberg http://en.

The idea of graphs is a very old and very interesting topic for mathematicians too. See http://en.wikipedia.org/wiki/Seven_Bridges_of_K%C3%B6nigsberg http://en.wikipedia.org/wiki/Seven_Bridges_of_K%C3%B6nigsber...