You will be given a definition of a task first, then some input of the task.
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 Sandra Taylor. 
 agent: Hello, how may I aid you? 
 customer: I want to change an existing reservation, can you please help me in that? 
 agent: Sure, I am here to help you. Please wait for a while. 
 customer: Sure. 
 agent: Thanks for your time, there is no active reservation found in your name. 
 customer: That's ok, not a problem. Thanks for your information. 
 agent: Thank you for choosing us.
Output:
no_reservation