def minimumAverage(customers):
    # Customers is a list of tuples. I assume it's already
    # sorted by i[0], the arrival time, but let's make sure.
    # We'll also need to know the total customer number in
    # order to calculate the average wait later on.
    
    customers.sort()
    cust_count = len(customers)
    
    # Since the minimum average wait will always be reached
    # by preparing the quickest pizza first, we want to store
    # the pizzas in a min heap sorted by required cook time.
    
    # As we start cooking, we'll pull customers off the list
    # and put them into a heap of waiting customers. We'll
    # also need to track time throughout the process to know
    # when to add to the heap or remove from it. And since
    # we're calculating average using the total number of
    # customers, we need a variable for total wait time to
    # divide by it.
    
    waiting = []
    time = 0
    wait_time = 0
    
    # This whole process will run until there are no more
    # customers in either list.
    
    while customers or waiting:
        
        # Move customers to waiting once they've ordered.
        # Flip tuple values for correct priority sort.
        while customers and time >= customers[0][0]:
            t_order, t_cook = customers.pop(0)
            heapq.heappush(waiting, (t_cook, t_order))
        
        # If we're waiting for orders, jump to the next.
        if len(waiting) == 0:
            time = customers[0][0]
            continue
        
        # We don't want to move one second at a time as
        # that would confuse priority. We want to think
        # of time in the form of pizzas cooked. So,
        # instead of incrementing time, we'll add the
        # cook time of the highest priority pizza, one at
        # a time. That will give the time the customer is
        # served, from which we subtract their order time
        # to know their wait and add it to the total wait.
        
        cook, order = heapq.heappop(waiting)
        time += cook
        wait_time += (time - order)
        
    # Use // to return only the integer part of avg time.
    return wait_time // cust_count