input: Write a python function to simulate Psychomotor Vigilance Task and calculate average response time.
  assert pv_task([500, 1500, 2500, 3500, 4500]) == 2000
  assert pv_task([1000, 2000, 3000, 4000, 5000]) == 3000
  assert pv_task([0, 100, 200, 300, 400, 500, 600, 700, 800, 900]) == 450
output: def pv_task(response_times):
      return sum(response_times) // len(response_times)