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: Hi. 
 agent: Hello. 
 customer: Stephen King here. 
 agent: How can I assist you today? 
 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: Sure. Please wait for a minute, let me check. 
 customer: Ok. 
 agent: Thank you for waiting, but I have not found any reservation by your name. 
 customer: That's ok. Thank you for the information. 
 agent: Thank you for contacting us, have a nice day.
Output:
no_reservation