while 1:
h,w = map(int, raw_input().split())
  if h==w==0
    break

for i in range(0,h/2):
  print ("#." * (w/2) + "#" * (w%2) + "\n")
  print (".#" * (w/2) + "." * (w%2) + "\n")

if h/2 == 1:
  print ("#." * (w/2) + "#" * (w%2) + "\n")