Definition: 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
Input: customer: Hello, I'm Carol Adams. 
 agent: Hello. Welcome to Global flight ticket booking agency. How can I help you Carol? 
 customer: Due to the postponement of a concert held in India, I would like to change my existing reservation. Can you please help me out? 
 agent: Sure, I will help you. 
 customer: Thank you. 
 agent: Please wait a moment. 
 customer: Ok. 
 agent: No previous reservation found on your name Carol Adams. 
 customer: That's ok, thank you. 
 agent: Do you want to know any thing else from us? 
 customer: No thanks. 
 agent: Thank you for contacting us, have a good day.
Output:
no_reservation