<Direction-performance>

<Solution-explanation>



<YOUKU_for chinese>

Performance - https: //v.youku.com/v_show/id_XNDI1MjAyMzg3Mg==.html ? spm=a2h3j.8428770.3416059.1

Explanation- https: //v.youku.com/v_show/id_XNDI1MjAyNTAwOA==.html?spm=a2h3j.8428770.3416059.1