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 am Nicholas Hall. 
 agent: Hello, how can I assist you for the day? 
 customer: I want to change my existing reservation due to postponed of my brother marriage. Can you please help me with this? 
 agent: Sure, I am here to help you. 
 customer: Thank you. 
 agent: Please wait for a moment. 
 customer: Sure. 
 agent: Sorry, we found no reservation on your given name. 
 customer: No problem, thanks for your information. 
 agent: Thank you for reaching us.
Output:
no_reservation