Hi everyone I was solving this problem. I tried a lot for finding a general formula for — How many permutation out of $$$n!$$$ will lead to exactly $$$K$$$ different chocolates. Then we just have to find probability by dividing with $$$n!$$$ and find Expectation by multiplying with $$$K$$$ and finally add the expectation for all such $$$K$$$ in range $$$[1,N]$$$. But I am unable to find a general formula for this. Also I am not able to get the editorial basically proof of that.
Can anyone please provide some idea regarding this. It'll be of great help.

Hi Almighty CF Community,

First I googled a lot but didn't get any explanation.(However code is available)

I feel it difficult to solve problems of type "no of ways to arrange some elements of chess so that they are attacking/not attacking each other." I was solving CSES Two Knights problem and I am struggling to come up by a general formula.

I will request if any one can explain the idea behind such problems in general? or at least for this Two Knights problem.

$$$If \,you\, know \,some \,chess \,based \,problems, \,I \,will\, request\, you \,to \,please \,share \,it. \,Thanks.$$$