while True:
   H, W = map(int, input().split())
   if H == 0 and W == 0:
      break
   for i in range(H/2):
      if W % 2 == 0:
         print("#." * (W/2))
      else:
         print("#."*(W/2) + "#")
      if W % 2 == 0
         print(".#" * (W/2))
      else:
         print(".#"*(W/2) + ".")
   if H % 2 != 0 
      if W % 2 == 0:
         print("#." * (W/2))
      else:
         print("#."*(W/2) + "#")
   print("")
