Give an example program for trees

def tree(n):
  if n == 0:
    return 0
  else:
    return n + tree(n-1)

def main():
  n = int(input("Enter a number: "))
  print(tree(n))

main()

A:

You can use recursion to solve this problem. The idea is to keep track of the current level of the tree and the current number of nodes at