A dredging zone is a grid of R rows and C columns. Each cell holds a non-negative amount of silt; a 0 marks barren mud the dredger cannot pass through. In one run the dredger may start on any cell that has silt greater than 0, and from its current cell it may step up, down, left, or right onto an adjacent cell whose silt is greater than 0. Each cell scooped is emptied, so a run may not visit the same cell twice. The dredger collects the silt of every cell it visits.
Determine the maximum total silt collectible in a single run. If every cell is barren, the answer is 0.
Input format
Line 1: two integers R and C.
Next R lines: each contains C non-negative integers, the silt amounts of that row.
Output format
A single integer: the maximum silt collectible in one run, or 0 if no cell has positive silt.
Constraints
- 1 <= R <= 5
- 1 <= C <= 5
- 0 <= each silt amount <= 100