K Smallest Elements from Two BSTs

You are given two binary search trees (BSTs) and an integer k. Your task is to find the k smallest elements from the union of these two BSTs. Input format: The first line contains the integer k (1 <= k <= 1000). The next line begins with an integer n (1 <= n <= 1000), the number of nodes in the first BST, followed by n lines each containing the node value and its left and right children. Then, a line with an integer m (1 <= m <= 1000) follows for the second BST, followed by m lines similar to the first BST. Output format: Print k smallest elements as a space-separated string. Example: Input: 3 3 4 2 5 2 1 -1 5 -1 -1 3 1 -1 -1 6 -1 -1 Output: 1 2 4