674. Cut Off Trees for Golf Event

In a forest grid, 0 is an impassable cell, 1 is walkable ground, and any value greater than 1 is a tree of that height. Starting at (0,0), you must cut trees in increasing height order, walking 4-directionally (a cut tree becomes ground). Return the minimum total steps to cut all trees, or -1 if some tree is unreachable. The input is JSON {forest}.

Input: JSON {forest}.

Output: Integer — the minimum total steps, or -1.

Examples

Input: {"forest":[[1,2,3],[0,0,4],[7,6,5]]}
Output: 6
Explanation: Walk the spiral cutting in order.

Input: {"forest":[[1,2,3],[0,0,0],[7,6,5]]}
Output: -1
Explanation: Lower row is unreachable.

Input: {"forest":[[2,3,4],[0,0,5],[8,7,6]]}
Output: 6
Explanation: Reachable in order.

Constraints

• 1<=rows,cols<=50

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