Container Water Accumulation

Given an array of building heights \(H = [h_0, h_1, \ldots, h_{n-1}]\), determine the total amount of water that can be collected between these buildings. For each building at index \(i\), the water accumulated above it is given by:

\(w_i = \max(0, L_i - h_i)\)

where \(L_i = \max_{0 \leq j < i} h_j\) is the maximum height among the buildings to its left. Note that the first building never accumulates any water.

Your task is to compute the sum \(\sum_{i=1}^{n-1} w_i\) which represents the total water collected.

inputFormat

The first line contains an integer n, the number of buildings.

The second line contains n space-separated integers representing the heights of the buildings.

outputFormat

Output a single integer representing the total amount of water collected.

6
3 1 2 4 2 3

6