Given the task definition and input, reply with output. 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. 
 agent: Hello. How can I assist you today? 
 customer: I am Mark Parker. I am planning to cancel my recent reservation, due to some work. Can you please cancel my ticket? 
 agent: Sure, please allow me a moment to check for the previous reservation. 
 customer: Sure, take your own time. 
 agent: Mark, there is no reservation found under your name. 
 customer: That's fine. Thank you for your service. 
 agent: Thank you for reaching us.
no_reservation