You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, you are given a conversation between a flight agent and the customer. You are given 4 options and you need to select the goal of the conversation. It is provided as part of customer's context, which has to be one of the following: `book`: Make a new reservation, `cancel`: Cancel an existing reservation, `no_flight`: No flight found for the customer's preference, `no_reservation`: No reservation / No change / No cancellation was made in the conversation, mostly enquiring details

customer: Hi. 
 agent: Hello. How can I help you? 
 customer: I would like to change my existing reservation as my plan to go for a holiday trip got postponed. Can you please help me with this? 
 agent: Sure, may I know your name please? 
 customer: My name is Anthony Phillips. 
 agent: Please wait a moment. 
 customer: Sure. 
 agent: Unfortunately there is no reservation found with your given name. 
 customer: Not a problem, thank you for checking. 
 agent: Thank you for choosing us.
Solution: no_reservation
Why? Here the customer has not asked for any booking, he just wanted to update his already booked flight, so the status would be no_reservation

New input: customer: Hello. 
 agent: Hello, how may I serve you? 
 customer: I am Ryan Thomas. I need a flight ticket to go to my hometown that is Chicago, can you please help me to book a flight ticket from Washington? 
 agent: Sure, can you please share your airport codes? 
 customer: Thank you. The preferred airport codes are DCA and ORD. 
 agent: When are you planning to travel? 
 customer: The planned travel dates are 12/10 and 12/12. 
 agent: Do you need a lay by? 
 customer: Yes, I need a single halt. 
 agent: Thanks for sharing your details. There are no flights found on your route. 
 customer: It's ok, thank you for searching the flight. 
 agent: Thank you for opting us. 
 customer: You are welcome.
Solution:
no_flight