# NOTE: just a dump from the phone screen.

class Node:
  def __init__(self, val):
     self.right = None
     self.left = None
     self.val = val

# Not perfect, if the n is not in tree then the biggest element of the tree is
# not returned.
#
# Or if the tree is just a root node, then it doesn't work (that edge case
# could be solved with a separate function for the recursion).
#
# (Also actually untested, but looks like it works)
     
def next_smallest(root, n):
  if root is None:
    return

  rv = next_smallest(root.left, n)
  if rv is not None:
    return rv
  
  if root.right == n:
    return root.val

  rv = next_smallest(root.right, n)
  if rv is not None:
    return rv
  return None