Mercury Poisoning

Kim has broken in to the base, but after walking in circles, perplexed by the unintelligible base design of the JSA, he has found himself in a large, empty, and pure white, room. The room is a grid with $H*W$ cells, divided into $H$ rows and $W$ columns. The cell $(i,j)$ is at height $A[i][j]$. Unfortunately, his advanced sense of smell has allowed him to sense a mercury leak, probably brought