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, my name is David Thompson. 
 agent: Hello David,. How can I help you now? 
 customer: Due to sudden change in weather where I wanted to visit, I need to cancel the ticket. 
 agent: Ok sure, please wait a moment. Thank you for waiting. Sorry David, no reservation is found under your name. Thank you for choosing us. 
 customer: Ok that's fine, thank you for giving a instantaneous response. 
 agent: You are welcome, have a good day.
Student:
no_reservation