I’m moving to another place. Right the next day I submitted the notice to the leasing office my kids, being under great impression of “Blue’s Clues” TV program, started playing clues. Soon they invented that the best clues can be made with marker on walls. I spent about 1 hour trying different substances on the walls, but the wall-marker combination was much stronger then Soap, Magic Eraser, OxiClean, rubbing alcohol and other pretty powerful substances. Only in a few weeks I recalled what I was studying on chemistry at school and solved the problem in seconds.