Water Filling in Containers

You are given $N$ containers of varying heights, $H_i$ for the $i^{th}$ container, which cannot hold more water than their heights. You have to fill water in these containers in such a way that the height of water filled in the $(i+1)^{th}$ container is $K$ more than the height of water filled in the $i^{th}$ container where $1 \leq i \leq N-1$. You need to find the maximum possible value of $K