int dx[4] = {-1, 0, 1, 0};

int dy[4] = {0, 1, 0, -1};

int bfs(int x, int y, int nextX, int nextY, vector<vector<int>>& forest, vector<vector<bool>>& visited) {

int n = (int) forest.size();

int m = (int)forest[0].size();

queue<pair<pair<int, int>, int>> Q;

Q.push({{x, y}, 0});

visited[x][y] = true;

while(!Q.empty()) {

pair<pair<int, int>, int>& front = Q.front();

int currX = front.first.first;

int currY = front.first.second;

int d = front.second;

if(currX == nextX and currY == nextY) {

return d;

}

for(int i = 0; i < 4; i++) {

int newX = currX + dx[i];

int newY = currY + dy[i];

if(newX >= 0 and newY >= 0 and newX < n and newY < m and forest[newX][newY] > 0 and !visited[newX][newY]) {

visited[newX][newY] = true;

Q.push({{newX, newY}, d + 1});

}

}

Q.pop();

}

return -1;

}

public:

int cutOffTree(vector<vector<int>>& forest) {

int n = (int)forest.size();

int m = (int)forest[0].size();

priority_queue<pair<int, pair<int, int>>, vector<pair<int, pair<int, int>>>, greater<pair<int, pair<int, int>>>> pQ;

for(int i = 0; i < n; i++) {

for(int j = 0; j < m; j++) {

if(forest[i][j] > 1) {

pQ.push({forest[i][j], {i, j}});

}

}

}

int x = 0, y = 0;

int minSteps = 0;

while(!pQ.empty()) {

pair<int, pair<int, int>> top = pQ.top();

int treeHeight = top.first;

int nextX = top.second.first;

int nextY = top.second.second;

pQ.pop();

vector<vector<bool>> visited(n, vector<bool>(m, false));

int distance = bfs(x, y, nextX, nextY, forest, visited);

if(distance == -1) {

return distance;

}

minSteps += distance;

x = nextX, y = nextY;

}

return minSteps;

}