input: Write a python function to generate a random integer between 1 and a raised to the power of b.
  assert 1 <= random_int(2, 3) <= 8
  assert 1 <= random_int(3, 2) <= 9
  assert 1 <= random_int(4, 2) <= 16
output: import random
  
  def random_int(a, b):
      return random.randint(1, a ** b)