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Zadanie Wieże (wie)
Rooks [B]
Memory limit: 32 MB
After quite a lot of effort Bytie has finally managed to put 
rooks
on a board of size 
so that no two of them attack each other.
A quick reminder: a rook attacks all the fields of the board that
are located in the same row or in the same column as it is1.
Unfortunately, the boy has now accidentally hit the board. As a result, several rooks have fallen down from it. Could you help Bytie put these rooks back on the board? The boy would like to leave the rooks that are still on the board intact.
Input
The first line of the standard input contains one integer 
(
) that represents the size of the board.
A description of the configuration of the rooks follows:
the following 
lines contain 
characters each.
The character '.' represents an empty field whereas
the letter 'W' represents a field occupied by a rook.
You can assume that there are 
rooks on the board with 
and that no pair of rooks on the board attacks each other.
Output
Your program should write to the standard output 
lines containing 
characters '.' or 'W' each: the final configuration of rooks on the board.
The description should contain exactly 
occurrences of the letter 'W'
with 
rooks placed in the same positions as in the initial board.
No two rooks may attack each other.
If there are multiple ways of placing 
rooks on the initial board, your program should output
any one of them.
Example
For the input data:
8 ........ .....W.. ..W..... .......W W....... ........ .W...... ........
the correct result is:
...W.... .....W.. ..W..... .......W W....... ....W... .W...... ......W.
Task author: Jakub Radoszewski.
1. See also http://en.wikipedia.org/wiki/Rook_(chess)