while 1:
   H, W = map(int, raw_input().split())
   if H == 0 and W == 0:
      break
   else:
      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 ("")