while True:
 h,w=map(int,input().split())
 if h==0:break
 for i in range(h):
  if i%2==0:print("".join(zip(['#']*((w+1)//2),['.']*(w//2))))
  else:print("".join(zip(['.']*((w+1)//2),['#']*(w//2))))
 print()