Enjoy the match!

There are $N$ football matches, numbered from $1$ to $N$, that you'd like to watch. The $i^{th}$ match has two values, i.e. $S_{i}$ and $R_{i}$, which represent the stadium number, and the number of good ratings of the stadium. You are going to watch these matches exactly once, and you can watch them in any order. The Enjoyment you get from a particular match is the product of its stadium's numbe