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