摘要：
D. Counting Rhyme You are given an array of integers $a_1, a_2, \ldots, a_n$. A pair of integers $(i, j)$, such that $1 \le i < j \le n$, is called go 阅读全文
摘要：
D. Doremy's Connecting Plan Doremy lives in a country consisting of $n$ cities numbered from $1$ to $n$, with $a_i$ people living in the $i$-th city. 阅读全文