input: def mod_exp(n: int, p: int):
      """Calculate 2 raised to the power of n, followed by taking the modulo p.
      >>> mod_exp(3, 5)
      3
      >>> mod_exp(1101, 101)
      2
      >>> mod_exp(0, 101)
      1
      >>> mod_exp(3, 11)
      8
      >>> mod_exp(100, 101)
      1
      """
output:     
      return (2 ** n) % p
  