class Solution {
    TreeNode res = new TreeNode();
    TreeNode curr=res;
    public TreeNode increasingBST(TreeNode root) {
        inOrder(root);
        return res.right;
    }
    
    public void inOrder(TreeNode root){
        if(root == null) return;
        inOrder(root.left);
        curr.right = new TreeNode(root.val);
        curr = curr.right;
        inOrder(root.right);
    }
}