Codeforces Round 800 (Div. 1)
D
Decinc Dividing
Codeforces
2800
原题
← CE →
翻译中…

Let's call an array $a$ of $m$ integers $a_1, a_2, \ldots, a_m$ Decinc if $a$ can be made increasing by removing a decreasing subsequence (possibly empty) from it.

翻译中…
  • For example, if $a = [3, 2, 4, 1, 5]$, we can remove the decreasing subsequence $[a_1, a_4]$ from $a$ and obtain $a = [2, 4, 5]$, which is increasing.
翻译中…

You are given a permutation $p$ of numbers from $1$ to $n$. Find the number of pairs of integers $(l, r)$ with $1 \le l \le r \le n$ such that $p[l \ldots r]$ (the subarray of $p$ from $l$ to $r$) is a Decinc array.

翻译中…

Input

翻译中…

The first line contains a single integer $n$ ($1 \le n \le 2 \cdot 10^5$)  — the size of $p$.

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The second line contains $n$ integers $p_1, p_2, \ldots, p_n$ ($1 \le p_i \le n$, all $p_i$ are distinct)  — elements of the permutation.

翻译中…

Output

翻译中…

Output the number of pairs of integers $(l, r)$ such that $p[l \ldots r]$ (the subarray of $p$ from $l$ to $r$) is a Decinc array. $(1 \le l \le r \le n)$

翻译中…

Note

翻译中…

In the first sample, all subarrays are Decinc.

翻译中…

In the second sample, all subarrays except $p[1 \ldots 6]$ and $p[2 \ldots 6]$ are Decinc.

翻译中…

样例

Input #1
3
2 3 1
Output #1
6
InputCopy OutputCopy
Input #2
6
4 5 2 6 1 3
Output #2
19
InputCopy OutputCopy
Input #3
10
7 10 1 8 3 9 2 4 6 5
Output #3
39
InputCopy OutputCopy
题目信息
题号
1693D
时间限制
2 s
内存限制
256 MB
标签
暴力
数据结构
分治
动态规划
贪心

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