Customer Service Queue

You are tasked with simulating a customer service queue for a call center. Each customer can either join the queue, be served, or leave without being served. Implement a program that maintains the queue and processes requests based on the following input format: Input: - The first line contains an integer n (1 ≤ n ≤ 1000), the number of requests. - The next n lines contain one of the following commands: 'JOIN <customer_id>' - to join the queue with a unique customer ID. 'SERVE' - to serve the front customer in the queue and remove them. 'LEAVE <customer_id>' - to remove a specific customer from the queue without serving them. Output: - Print the customer IDs of the customers served in the order they were served. If the queue is empty when a SERVE command is encountered, print 'No customers in queue'. Example: Input: 5 JOIN 101 JOIN 102 SERVE LEAVE 101 SERVE Output: 102