I-Inverse Pair_2021牛客暑期多校训练营4

时间限制：C/C++/Rust/Pascal 1秒，其他语言2秒
空间限制：C/C++/Rust/Pascal 256 M，其他语言512 M
64bit IO Format: %lld

题目描述

For a sequence $t_{1...n}$ , we define the weight of it is the number of pairs $(i,j)$ satisfy $i<j$ and $t_i>t_j$ .

Now give you a permutation $a_{1...n}$ , you need to choose a sequence $b_{1...n}$ satisfies $b_i\in \{0,1\}$ to minimize the weight of sequence $c_{1...n}$ which satisfies $c_i=a_i+b_i$ .

输入描述:

The first line has one integer .

The second line has  integers .

It's guaranteed that  is a permutation of

输出描述:

Output the minimum weight of  you can get.

示例1

输入

复制

5
4 3 2 5 1

输出

复制