RAIN WATER SAVING-INTERVIEW QUESTION (FAANG)

AKSHITA has created an elevated roof. She wants to know how much water can she save during rain.

Given n non negative integers representing the elevation map where width of every bar is 1, Find the maximum water that she can save.

Explanation for the Sample input Testcase:

Elevation Map
Input Format

First line contains an integer n. Second line contains n space separated integers representing the elevation map.
Constraints

1 <= N <= 10^6
Output Format

Print a single integer containing the maximum unit of waters she can save.
Sample Input

10
0 2 1 3 0 1 2 1 2 1

Sample Output

5