Corporate Subtree Budget

A company uses IDs to represent employee seniority in a BST. Each ID is also its budget. Given a target value X, first find the 'Anchor Node', which is the node with the smallest ID such that ID >= X. If such a node exists, calculate the sum of all IDs in the subtree rooted at that Anchor Node. If no such node exists, output 0. Example: Input: 5 2 8 1 3; 2 Output: 6 Explanation: The smallest ID >= 2 is 2. The subtree at 2 includes 2, 1, and 3. Sum: 2+1+3 = 6.