while 1:
  H,W = map(int,input().split())
  if H == W == 0:
    break
  else:
    for i in range(H):
      for j in range(W):
        if  (i + j) % 2 == 0:
          print("#",end='')
        else:
          print(".",end='')
      print()
    print()
