The answer, in my case, is ten.
In Japan, people are traditionally accustomed to sitting on the floor, so when one of my lightbulbs blew last night, I found my furnished apartment lacking a chair high-enough to stand on while I changed it.
Today, though, some lateral thinking led me to make use of a stack of ten comic books that I’d rescued from the garbage area about two weeks ago. Weekly comic compilations in Japan are _very_ thick, so the bundle of ten, neatly tied up with string for collection, was quite high enough for me to reach the light fitting.
Ten comic books, next to one of the floor-sitting chairs that were in my apartment when I arrived.