摘要：
D. Lonely Mountain Dungeons Once, the people, elves, dwarves, and other inhabitants of Middle-earth gathered to reclaim the treasures stolen from them 阅读全文
摘要：
E. Space Harbour There are $n$ points numbered $1$ to $n$ on a straight line. Initially, there are $m$ harbours. The $i$-th harbour is at point $X_i$ 阅读全文