Given an array A that is a permutation of n numbers [1-n]. Find the number of subarrarys S that meets the following condition max(S) - min(S) = length(S) - 1.

Example 1:

Input: [4, 3, 1, 2, 5]
Output: 10
Explanation:
subarrays that meets the condition are
[4]
[3]
[1]
[2]
[5]
[4 3]
[1 2]
[3 1 2]
[4 3 1 2]
[4 3 1 2 5]

There are 10 subarray that meets the condition, so the answer should be 10.

Is there a better than O(n^2) solution?