3D Surface Area

2D grid A[i][j] = height (cubes) at cell (i,j). Calculate total surface area of the 3D shape. Formula: Top + Bottom + 4 sides. For each cell: top=1, bottom=1, each side = max(0, height - neighbor_height) if neighbor exists, else = height. Sum all faces. Example: Grid [[1,3,4],[2,2,3],[1,2,4]] → Calculate exposed faces for each cell and sum.

Input

First line: H W (space-separated). Next H lines: W space-separated integers each.

Output

A single integer: the total surface area.

Sample

3 3
1 3 4
2 2 3
1 2 4

Expected

60