class Node:

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

self.val = val

self.left = left

self.right = right

def inorder(root):

res = []

if not root:

return res

stack = []

while root or stack:

while root:

stack.append(root)

root = root.left

root = stack.pop()

res.append(root.val)

root = root.right

return res

if __name__ == '__main__':

n1 = Node(100)

n2 = Node(50)

n3 = Node(150)

n4 = Node(25)

n5 = Node(75)

n6 = Node(125)

n7 = Node(175)

n1.left, n1.right = n2, n3

n2.left, n2.right = n4, n5

n3.left, n3.right = n6, n7

print(inorder(n1))