Bread Rolls Stock Tracker

A bakery needs a program to make sure there are always enough fresh bread rolls available. The bakery starts with a stock of 50 bread rolls. The program should repeatedly take in the number of rolls sold until a value of -1 is entered.

Whenever the stock falls below 20, the program should output "Add new stock" and add 50 to the current stock. When -1 is entered, the program should stop and output the total number of rolls sold.

Input: A sequence of integers representing rolls sold, ending with -1. Output: "Add new stock" each time stock drops below 20, then the total rolls sold at the end.

Example:

Input:  24
        12
        -1
Output: Add new stock
        36