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: Hello. I am Robert Collins. 
 agent: Hello, how may I assist you for today? 
 customer: I am planning to attend my friend's marriage at Dallas, can you please help me to book a flight with single connection? 
 agent: Sure, I am happy to help you. When you have planned your journey? 
 customer: I am planning to travelling on 07/09 to 07/11. 
 agent: Ok, can you please mention your source and destination codes of journey? 
 customer: I would like to fly from PHL-DFW. 
 agent: I apologize for the inconvenience, there is no flights to your destination from our service. 
 customer: Ok, no issues, thanks for your information. 
 agent: Thank you for opting our service. Have a good day. 
 customer: Thank you.
Output:
no_flight