Have you ever played Minesweeper? It is a cute little game which comes

within a certain Operating System which name we cannot really remember.

Well, the goal of the game is to find where are all the mines within a MxN

field. To help you, the game shows a number in a square which tells you

how many mines there are adjacent to that square. For instance, suppose

the following $4$x$4$ field with $2$ mines $($which are represented by an $*$

character$)$:

$*...$

$....$

$.*..$

$....$