while 1:
  H, W = map(int, raw_input().split())
  if H == 0 and W == 0:
    break
  else:
    for h in range(H):
      for w in range(W):
        if (h + w) % 2 == 0:
          print "#",
        else:
          print ".",
      print ""
  print ""
 
  