P4749 [CF1693D] Decinc Dividing
NOI
题目描述

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.

  • 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.

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.

Input

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

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.

Output

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. $(1 \le l \le r \le n)$

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 2 3 1
样例输出
6
提示

In the first sample, all subarrays are Decinc.

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