Given the task definition and input, reply with output. 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: Hello, I am Thomas Young. 
 agent: Hello Thomas Young. How can I help you today? 
 customer: I have planned a trip with my friends, can you help in the process of booking ticket. 
 agent: Sure, can you provide me your travellings details? 
 customer: My travelling is from San Francisco, CA - SFO to Detroit, MI - DTW. My travelling dates are on 04/24 to 04/26. 
 agent: Sure, wait for a moment, I will revert you. 
 customer: I need a single connection with price of 5000. Sure,. 
 agent: Thanks for waiting. We could not find any flights for your specification. 
 customer: OK, thank you for the information. Thank you. 
 agent: Thank you for reaching us.
no_flight