Chain Reaction

You are given a grid with $R$ rows (numbered $1$ through $R$) and $C$ columns (numbered $1$ through $C$). A cell in row $r$ and column $c$ is denoted by $(r, c)$. Two cells in the grid are adjacent if they have a common side. For each valid $i$ and $j$, there is a value $a_{i, j}$ written in cell $a_{i, j}$. A cell in the grid is *stable* if the number of cells in the grid which are adjacent to