摘要：
题目链接 Problem Description As we know, Rikka is poor at math. Yuta is worrying about this situation, so he gives Rikka some math tasks to practice. Ther 阅读全文
摘要：
题目链接 Problem Description There is a set including all positive integers that are not more then n. HazelFan wants to choose some integers from this set 阅读全文