595. Trapping Rain Water II

0

Hard

Given an m x n integer matrix heightMap representing the height of each unit cell in a 2D elevation map, Print the volume of water it can trap after raining.

Input Format

First line contains Number of Rows
Second line contains Number of Columns
Third line contains elements of matrix

Output Format

Print volume (Integer)

Example

Input

3 6 1 4 3 1 3 2 3 2 1 3 2 4 2 3 3 2 3 1

Output

4

Constraints

m == heightMap.length
n == heightMap[i].length
1 <= m, n <= 200
0 <= heightMap[i][j] <= 2 * 104
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