Practice problem
Pigeonhole Principle
Whiteboard Principle
There are four colors of whiteboard markers, but unfortunately, markers run out quickly. Every night, the custodian makes sure that there are 10 markers in the room, but he doesn't pay attention to what colors they are.
I'd like to teach my first class using just one color. Fortunately, I can be sure that some color will have at least ___ markers. Fill in the blank. Please enter the biggest number for which the statement is still true.