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

def level_order(root):


if __name__ == "__main__":
    a = Node(1)
    b = Node(2)
    c = Node(3)
    d = Node(4)
    e = Node(5)

    a.left = b
    a.right = c
    b.left = d
    b.right = e


