Teacher: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
Teacher: Now, understand the problem? Solve this instance: customer: Hello, I am Jack Robinson. 
 agent: Hello, how may I assist you today? 
 customer: Can you please help me in booking my flight ticket from PHL to EWR? 
 agent: Sure, may I know your trip dates please? 
 customer: My planned trip dates are Nov 21-23. 
 agent: Do you have any specifications? 
 customer: I need a direct flight. 
 agent: Sorry, there are no flights found with your given details. 
 customer: Ok, no issues. Thank you. 
 agent: Thank you for reaching us.
Student:
no_flight