. (1米)
- (10米)
----------(100米)
--------------------------------------------------------------------------------------------------(1000米)
--------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------(10000米)
别以为走一米容易,走一万米就简单。走过一万米了,两万米会难吗。。又不是开灰机!~