Detailed Instructions: 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
Q: customer: Hi. I am Laura Turner. 
 agent: Hello, How can I serve you? 
 customer: I want to fly with the direct flight from Washington to attend an interview in Philadelphia, can you help me to book an economy class ticket? 
 agent: Sure, May I know the travel dates? 
 customer: I intend to start on Nov 28th and I will return within two days that is on Nov 30th. 
 agent: Please help me with your journey codes. 
 customer: My source and destination airport code are IAD and PHL. 
 agent: Please wait a minute. 
 customer: Sure. 
 agent: Sorry, No flights found with your chosen dates. 
 customer: No issues, I'll choose any alternative to reach my destination. Thank you. 
 agent: Thank you for opting us.
A:
no_flight