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, Jerry Smith is my name. 
 agent: Hello, how may I help you? 
 customer: Having the NHL Stanley Cup Playoffs at San Francisco, SFO. I would like to book a ticket. Could you help me in booking a flight ticket on 12/02? 
 agent: Sure, may I know your return date? 
 customer: 12/04 is my return date. 
 agent: Kindly provide your source code. 
 customer: Source code: Las Vegas, LAS. 
 agent: Unfortunately there is no flight found matching with your requirements. 
 customer: Ok, no problem. Thank you for your quick response. 
 agent: Thank you for reaching us.
no_flight