Hi, here's your problem today. This problem was recently asked by Twitter:

Given a tree, find if the binary tree is height balanced or not. A height balanced binary tree is a tree where every node's 2 subtree do not differ in height by more than 1.

Here's some starter code:

```
class Node:
def __init__(self, value, left=None, right=None):
self.value = value
self.left = left
self.right = right
def is_height_balanced(tree):
# Fill this in.
# 1
# / \
# 2 3
# /
# 4
n4 = Node(4)
n3 = Node(3)
n2 = Node(2, n4)
n1 = Node(1, n2, n3)
print(is_height_balanced(n1))
# True
# 1
# /
# 2
# /
# 4
n1 = Node(1, n2)
print(is_height_balanced(n1))
# False
```