#define pathSum(root) __pathSum(root, 0)

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
int __pathSum(struct TreeNode* root, int depth) {
  if (!root) return 0;
  if (!root->left && !root->right)
    return root->val * depth;
  return __pathSum(root->left, depth + 1) + 
         __pathSum(root->right, depth + 1);
}