Let's say that you have x different stocks, and the plots of their prices over time. You want to print them in newspaper, printing multiple plots on the same chart to save space. But here's the catch: no two plots on the same chart can overlap, lest the readers be confused. Look at the plots and figure out the smallest number of charts required. Looking for a challenge like the riddle above? And I mean an exciting brain-twisting and turning kind of challenge.