题目描述
Problem Statement
You are given $a permutation P=(P_1,P_2,\cdots,P_N)$ of $(1,2,\cdots,N)$.
You want to perform zero or more swaps of adjacent elements so that P satisfies the following condition:
- The number of indices i such that P_i > P_{i+1} is at most 1.
Find the minimum number of swaps required.
Input
The input is given from Standard Input in the following format:
N
$P_1 P_2 \cdots P_N$
Output
Print the answer.
Constraints
- $2 \leq N \leq 800000$
- $(P_1,P_2,\cdots,P_N)$ is a permutation of $(1,2,\cdots,N)$.
- All input values are integers.
Sample Input 1
3
3 2 1
Sample Output 1
1
Swapping P_1 and P_2 turns P into (2,3,1), which satisfies the condition.
Sample Input 2
4
2 4 1 3
Sample Output 2
0
Sample Input 3
6
2 3 1 6 4 5
Sample Output 3
1
Sample Input 4
20
8 13 6 11 20 3 12 18 17 4 10 1 7 16 19 5 2 15 14 9
Sample Output 4
36
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
3
3 2 1
样例输出
1