input: Write a function to solve the Tower of Hanoi problem.
  assert hanoi(1, 'A', 'B', 'C')==None
  assert hanoi(2, 'A', 'B', 'C')==None
  assert hanoi(3, 'A', 'B', 'C')==None
output: def hanoi(n, source, auxiliary, target):
      if n > 0:
          hanoi(n - 1, source, target, auxiliary)
          print(f"Move disk {n} from {source} to {target}")
          hanoi(n - 1, auxiliary, source, target)