Write a program that prints a chessboard with N rows and M columns with the following rules:
The top left cell must be an asterisk (*)
Any cell touching (left, right, up or down) a cell with an asterisk must be a dot (.)
Any cell touching (left, right, up or down) a cell with a dot must be an asterisk.

A chessboard of 8 rows and 8 columns printed using these rules would be:
```
*.*.*.*.
.*.*.*.*
*.*.*.*.
.*.*.*.*
*.*.*.*.
.*.*.*.*
*.*.*.*.
.*.*.*.*
```
Input

A single line with two integers N and M separated by space. The number N will represent the number of rows and M the number of columns.

Output

Return N lines each containing M characters with the chessboard pattern.
Empty string if N, M or both are 0.


From: 2016 AIPO National Finals
http://aipo.computing.dcu.ie/2016-aipo-national-finals-problems

Difficulty: EASY
Starter code: def chessboard(s):
	

Solutions:
def chessboard(s):
	(N, M) = map(int, s.split())
	row = '.*' * M
	return '\n'.join([row[:M] if i & 1 else row[1:M + 1] for i in range(N)])


chessboard = lambda s: '\n'.join([''.join(['.' if (x + y) % 2 else '*' for x in range(int(s.split()[1]))]) for y in range(int(s.split()[0]))])


from itertools import cycle, islice

def chessboard(s):
	(n, m) = (int(a) for a in s.split())
	if not n or not m:
		return ''
	return '\n'.join(islice(cycle((''.join(islice(cycle('*.'), m)), ''.join(islice(cycle('.*'), m)))), n))


def chessboard(st):
	(height, width) = map(int, st.split())
	if height == 0 or width == 0:
		return ''
	board = [['*.'[x + y & 1] for x in range(width)] for y in range(height)]
	return '\n'.join(map(''.join, board))


def chessboard(s):
	(rows, cols) = map(int, s.split())
	if rows and cols:
		return '\n'.join((''.join(('*.'[(i + j) % 2] for i in range(cols))) for j in range(rows)))
	return ''


def chessboard(s):
	(a, b) = map(int, s.split())
	return '\n'.join((('*.' * (b + 1))[i & 1:(i & 1) + b] for i in range(a)))


def chessboard(s):
	(row, column) = [int(num) for num in s.split()]
	return '\n'.join((''.join(('*.'[(i + j) % 2] for j in range(column))) for i in range(row)))


def chessboard(s):
	(w, h) = map(int, s.split())
	return '\n'.join((''.join(('*.'[(i + j) % 2] for i in range(h))) for j in range(w)))


def chessboard(s):
	(m, n) = map(int, s.split())
	return '\n'.join((('*.' * n)[i % 2:n + i % 2] for i in range(m)))


def chessboard(s):
	(r, c) = map(int, s.split())
	return '\n'.join((''.join(('*.'[j % 2 != i % 2] for j in range(c))) for i in range(r)))