A fitness tracker application needs to convert running distances from kilometers to miles.
Review the following code:
def calculate_miles(kilometers):
miles = kilometers * 0.621371
return round(miles, 2)
km_run = float(input("Enter distance in km: "))
miles_run = calculate_miles(km_run)
print("Distance in miles: " + str(miles_run))
Identify the name of one built-in subprogram used in this code.