There is a step in a proof I don't understand.
$(\prod_{i\in K} p_{i}^{min(a_{i},b_{i})})\cdot (\prod_{i\in K, 1\leq i\leq k} p_{i}^{min(a_{i},b_{i})}) = \prod_{1\leq i\leq k} p_{i}^{min(a_{i},b_{i})}$
I'm not so sure what $\prod_{i\in K}$ and $\prod_{i\in K, 1\leq i\leq k}$ means.
Is there someone who can explain what is going on?