while 1:
   H, W = map(int, raw_input().split())
       
   if H == 0 and W == 0:
      break
   for i in range(H):
      if i%2 == 0:
         if W%2 == 1:
            print "#."*(w/2)+"#"
         elif W%2 == 0:
            print "#."*(W/2)
      elif i%2 == 1:
         if W%2 == 1:
            print ".#"*(w/2)+"."
         elif W%2 == 0:
            print ".#"*(W/2)

   print ""