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: Hi. 
 agent: Hello, how can I help you? 
 customer: Can you please help me in changing my reservation? 
 agent: Yes, I am here to help you. May I know your name please? 
 customer: I am Ruth Evans. 
 agent: Ok, please wait a minute I will get back to you. 
 customer: Ok. 
 agent: Thank you for your time, sorry no reservation found on your name. 
 customer: Ok, no problem. Thank you. 
 agent: Thank you for reaching us, have a nice day.
no_reservation