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, myself Robert Davis. 
 agent: Hello Davis. 
 customer: I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me? 
 agent: How can I help you today? Sure Davis. To make changes, I did not found any reservations with your name. 
 customer: No problem. 
 agent: Thank you for contacting us. 
 customer: You are welcome.
Output:
no_reservation