Queue Simulation for Customer Service

You are tasked with simulating a customer service queue in a bank. You will be given a sequence of customer arrival times and their service times. Your goal is to determine the total time when all customers have been served. Customers are served in a FIFO manner. Input Format: - The first line contains an integer N (1 <= N <= 1000), the number of customers. - The next N lines each contain two integers: arrival_time (0 <= arrival_time <= 10000) and service_time (1 <= service_time <= 1000). Output Format: - A single integer representing the total time when all customers have been served. Example: Input: 5 0 10 2 5 4 7 8 3 9 6 Output: 21