A12661. Special Segments of Permutation

You are given a permutation $p$ of $n$ integers $1$ , $2$ , ..., $n$ (a permutation is an array where each element from $1$ to $n$ occurs exactly once).

Let's call some subsegment $p[l, r]$ of this permutation special if $p_l + p_r = \max \limits_{i = l}^{r} p_i$ . Please calculate the number of special subsegments.

The first line contains one integer $n$ ( $3 \le n \le 2 \cdot 10^5$ ).

The second line contains $n$ integers $p_1$ , $p_2$ , ..., $p_n$ ( $1 \le p_i \le n$ ). All these integers are pairwise distinct.

Print the number of special subsegments of the given permutation.

Special subsegments in the first example are $[1, 5]$ and $[1, 3]$ .

The only special subsegment in the second example is $[1, 3]$ .