
import sys

if sys.platform == 'ios':
	sys.stdin=open('input_file.txt')
	
while True:
	H,W=map(int,input().split())
	
	if H+W==0:
		break
	for i in range(H):
		for j in range(W):
			print("#."[(i+j)%2],end="")
		print()
	print()
