You will be given a definition of a task first, then some input of the task.
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, Joshua Green here. 
 agent: Hello, how can I help you today? 
 customer: I am planning to book a flight in the afternoon time on 6th of Sept to reach Seattle, so please help me in booking a normal-cost flight. 
 agent: Sure, may I know your source and destination airport codes? 
 customer: Sure, my source and destination airport codes are DCA - SEA. 
 agent: May I know your return date? 
 customer: Sure, I intend to return on 8th of Sept. 
 agent: Do you need halt in between your journey? 
 customer: Yes, I prefer it. 
 agent: Ok, please wait for a moment. 
 customer: Sure. 
 agent: Sorry, there are no flights found with your given dates. 
 customer: No worries, thank you for informing me. 
 agent: Thank you for opting us.
Output:
no_flight