struct Path
{
    Node * root; // the highest vertex in this path
    int score;
    Path(Node * n = NULL, int s = 0)
      : root(n), score(s) {}
};

struct Return
{
    Path arm; // a path that is left or right arm of future best path
    Path best;  // complete subtree with the best score down below current node
};


Return maxSum(Node * n)
{
	if(!n) { return Return(); }
	Return L = maxSum(n->left);
	Return R = maxSum(n->right);

}