**题目地址：** [题目地址](http://acm.hhu.edu.cn/problemset.php?search=%E7%AC%AC%E5%85%AD%E5%B1%8A%E6%B2%B3%E6%B5%B7%E5%A4%A7%E5%AD%A6%E7%A8%8B%E5%BA%8F%E8%AE%BE%E8%AE%A1%E5%A4%A7%E8%B5%9B%EF%BC%88%E4%BD%8E...
**原题地址：** [原题地址](http://acm.hdu.edu.cn/search.php?field=problem&key=%A1%B0%D7%D6%BD%DA%CC%F8%B6%AF-%CE%C4%D4%B6%D6%AA%D0%D0%B1%AD%A1%B1%B9%E3%B6%AB%B9%A4%D2%B5%B4%F3%D1%A7%B5%DA%CA%AE%CB%C4%BD%EC%...