# -*- coding: utf-8 -*-

def main():

	while True:
		H,W = map(int,raw_input().split())
		if H == W == 0:
			break
		a = ''
		b = ''
		for i in xrange(W):
			if i % 2 == 0:
				a += '#'
				b += '.'
			else:
				a += '.'
				b += '#'
		for i in xrange(H):
			if i % 2 == 0:
				print(a)
			else:
				print(b)
		print('')

if __name__ == "__main__":

	main()
