Game of life (1)

The English mathematician John Conway invented in 1970 the following game: Imagine a matrix with $n$ rows and $m$ columns. We consider neighbor positions to a given position the (at most, eight) adjacent positions, either horizontally, vertically or diagonally. Every moment, each position is either empty or it contains a bacterium. The rules are:

An empty position at time $t$ will contain a bacterium at time $t + 1$ if and only if at time $t$ it had exactly three neighbor bacteria.
An occupied position at time $t$ will contain a bacterium at time $t + 1$ if and only if at time $t$ it had two or three neighbor bacteria.

Write a program that, for every given matrix, prints it at the next moment of time.

Input

Input consists of several cases. Every case begins with $n$ and $m$ (both strictly positive), followed by $n$ lines, each one with $m$ characters: ‘B’ if the position has a bacterium, and ‘.’ if the position is empty. A special case with $n = m = 0$ marks the end of the input.

Output

For each case, print the matrix corresponding to the next moment of time using the same format of the input (do not print $n$ and $m$ ). Separate matrices with an empty line.

Problem information

Author: Unknown
Translator: Carlos Molina

Generation: 2026-01-25T10:28:06.981Z