Challenge 0002: Minesweeper

[dcordero]

Have you ever played Minesweeper? This cute little game comes with a certain operating system whose name we can't remember. The goal of the game is to find where all the mines are located within a M x N field.
The game shows a number in a square which tells you how many mines there are adjacent to that square. Each square has at most eight adjacent squares. The 4 x 4 field on the left contains two mines, each represented by a '*' character. If we represent the same field by the hint numbers described above, we end up with the field on the right:

*...
....
.*..
....

*100
2210
1*10
1110

Input

The input will consist in a couple of integers n and m (0 < n, m <= 100) which stand for the number of lines and columns of the field, respectively. Followed by a matrix which contains exactly the characters representing the field.
Safe squares are denoted by "." and mine squares by "*", both without the quotes.

Output

A matrix replacing all the "." characters by the number of mines adjacent to that square.

Sample Results

Input   Output
4 4     
*...    *100
....    2210
.*..    1*10
....    1110

Input   Output
3 5
**...    **100
.....    33200
.*...    1*100

Disclaimer

This problem appeared originally in programming-challenges.com