例子：

$x\times y=\sum\limits_{i=1}^x\sum\limits_{j=1}^y\min{\left(\left\lfloor\frac{n}{i}\right\rfloor,\left\lfloor\frac{n}{j}\right\rfloor\right)} [\gcd{(i,j)}=1]$

$\max{S}=\sum_{T\subseteq S}{(-1)^{|T|-1}\min{T}}$