Once upon a time there was a very large office building in a very large city. This building had 40 levels: level 1, level 2, level 3, level 4, level 5, level 6, level 7, level 8, level 9, level 10, level 11, level 12, level 13, level 14, level 15, level 16, level 17, level 18, level 19, level...