A machine has 2 fuses that it needs to work. The fuses are identical and you cannot tell by looking or test if it's good in any other way. It doesn't matter which fuse goes where.
Assume I have N total fuses, and m of those are good.
Each time, I insert the 2 fuses into the machine and try to turn it on. If it doesn't, I use a different combination of fuses.
How do I find the least number of combinations that need to be tried in order to ensure that the machine turns on?