input: Write a function to calculate the average of five numbers entered by a user. The function should take five integers as input, calculate their average, and return the result as a float.
  assert calculate_average(10, 20, 30, 40, 50)==30.0
  assert calculate_average(5, 15, 25, 35, 45)==25.0
  assert calculate_average(2, 4, 6, 8, 10)==6.0
  assert calculate_average(1, 3, 5, 7, 9)==5.0
  assert calculate_average(100, 200, 300, 400, 500)==300.0
output: def calculate_average(a, b, c, d, e):
      return (a + b + c + d + e) / 5.0