while True:
   H, W = map(int, input().split())

   if H == 0 and W == 0:
      break

   for i in range(H/2):
      if H % 2 == 0:
         for j in range(W/2):
            if W % 2 == 0:
               print("#." * (W/2))
               print("")
               print(".#" * (W/2))
            else:
               print("#."*(W/2) + "#")
               print("")
               print(".#"*(W/2) + ".")
         print("")

      else:
         for j in range(W/2):
            if W % 2 == 0:
               print("#." * (W/2))
               print("")
               print(".#" * (W/2))
            else:
               print("#."*(W/2) + "#")
               print("")
               print(".#"*(W/2) + ".")
         if W % 2 == 0:
            print("#." * (W/2))
         else:
            print("#."*(W/2) + "#")
         print("")
