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: Hello, my name is Katherine Miller. 
 agent: Hello, Katherine Miller. How can I assist you? 
 customer: I am planning to spend my vacation holidays with my brother, so I need to make a flight reservation. 
 agent: OK, what is your exact destination and when do you want to go? 
 customer: My destination airport is PA-PHL, and my travelling dates are departure on 03/20 and arrival on 03/22. 
 agent: Let me know your source point. 
 customer: My source airport is San Francisco, CA-SFO. 
 agent: Sorry to inform, no flights are found regarding to your specifications. 
 customer: That's not a problem, thanks for your information. 
 agent: Thanks for choosing us. Have a great day.
A:
no_flight