Given the task definition and input, reply with output. In this task, you're given a dialogue between a customer and a flight booking agent with a gap in the conversation. Your job is to find the answer of the previous dialogue. Avoid using irrelevant extra information while creating the answer. The answer should be relevant to the question before the blank. If you fill the blank with a question, it should have an answer from the agent in the given dialogue. Fill the gap marked with underline.

customer: Hello. 
 agent: Hello. 
 customer: I am Laura Wright. 
 agent: Can you please let me know how may I help you? 
 customer: I would like to book a ticket to Washington DC , can you please help me in booking? 
 agent: Sure, I am here to help you. Will you please share your travelling dates? 
 customer: I am travelling on these dates 11/18 and 11/20. 
 agent: Ok, can you please mention the source and destination airport codes? 
 __ 
 agent: Ok, I found a flight AA airlines with connection limit 1 and the price is 100. Can I reserve your ticket? 
 customer: Sure, you can proceed with this flight. 
 agent: Ok, your ticket is booked with the flight number 1028. 
 customer: Thank you for your services. 
 agent: You are welcome. Thank you for choosing us.

customer: I am flying from HOU to DCA.