[ZJ][dp] a564. ITSA201205 P4 Group without direct leaders
內容
：
In X company, everyone,
except the CEO, has a direct leader. There are n persons in the company
and everyone has a unique ID from 0 to n-1. The ID of the CEO is 0, and
the ID of any one is larger than the one of his/her direct leader.
Besi...
