input: Write a python function to count the number of elements in a list that are greater than a given number.
  assert count_elements_greater_than([1, 2, 3, 4, 5], 3) == 2
  assert count_elements_greater_than([10, 20, 30, 40, 50], 25) == 3
  assert count_elements_greater_than([0, -1, -2, -3, -4], -3) == 2
output: def count_elements_greater_than(lst, num):
      return sum(1 for x in lst if x > num)