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