Instructions: 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
Input: customer: Hi. 
 agent: Hello, how may I help you? 
 customer: Please book a ticket from IAD to BOS. 
 agent: Sure, can I know your travelling dates? 
 customer: Travelling dates are Dec 28 and Dec 30. 
 agent: Sorry, there are no flights are available for given dates. 
 customer: Thank you. 
 agent: Thank you for reaching us. Can I know your name. 
 customer: I am Jeffrey Edwards.
Output:
no_flight