There are $N$ chess players of different strengths. If two of them play, the stronger one always wins.

There are $N$ chess players of different strengths. If two of them play,
the stronger one always wins.

What is the minimum number of games they need to play for us to determine
the order of their strengths?
I was asked this question for $N=5$ and I got 5 rounds, but I'm not sure
how to generalize it to any $N$. Thanks for any help.