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. 
 agent: Hello. How may I help you? 
 customer: I would like to travel from IAD to OAK as a business trip. Can you do the reservation? 
 agent: Sure, may I know your depart and arrival dates? 
 customer: My journey dates are 10/06 and 10/08. 
 agent: Do you have any connection limit? 
 customer: I need break in my journey. 
 agent: Is there any class preference? 
 customer: I am comfortable with economy class. 
 agent: Any other specifications to be met? 
 customer: My departure time should be evening. 
 agent: May I know your name? 
 customer: Samuel White here. 
 agent: Sorry, there were no flights found on your route. 
 customer: No problem, Thanks for the information. 
 agent: Thank you.
no_flight