'''
There is a queue for the self-checkout tills at the supermarket. Your task is write a function to calculate the total time required for all the customers to check out!

input
customers: an array of positive integers representing the queue. Each integer represents a customer, and its value is the amount of time they require to check out.
n: a positive integer, the number of checkout tills.
'''
def queue_time(customers, n):
    tills = [0]*n
    for i in customers:
      tills[0] += i
      tills.sort()
    return max(tills)
