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. 
 agent: Hello! tell me how may I help you? 
 customer: Can you help me to change my existing reservation? 
 agent: OK, can you please tell me your name ? 
 customer: Yes, my name is William Thompson. 
 agent: Sorry, William  no reservation found on your name. 
 customer: Ok, thank you. 
 agent: Thank you.
Output:
no_reservation