We are given an array A of positive integers, and two positive integers L and R (L <= R).
Return the number of (contiguous, non-empty) subarrays such that the value of the maximum array element in that subarray is at least L and at most R.
Example : Input: A = [2, 1, 4, 3] L = 2 R = 3 Output: 3 Explanation: There are three subarrays that meet the requirements: [2], [2, 1], [3].
Note:
<li>L, R and <code>A[i]</code> will be an integer in the range <code>[0, 10^9]</code>.</li>
<li>The length of <code>A</code> will be in the range of <code>[1, 50000]</code>.</li>