Forest Path Finder

Given a grid representing a forest where '1' represents trees and '0' represents open paths, find the longest path from the top-left corner (0,0) to the bottom-right corner (n-1,m-1) without stepping on any trees. You can only move right, down, left, or up. If there's no valid path, return -1. Input: - First line contains two integers n, m (1 <= n, m <= 100). - Next n lines, each containing m integers (0 or 1), representing the grid. Output: - A single integer representing the length of the longest path found or -1 if no path exists. Example: Input: 3 3 0 0 0 1 1 0 0 0 0 Output: 6