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, I am Charles Jackson. 
 agent: Hello, how can I assist you? 
 customer: Please help me in booking my flight ticket from BOS to PHX for my alumni meet? 
 agent: sure, when are you planning to move? 
 customer: My journey is from 07/01 to 07/03. 
 agent: Let me know your specifications? 
 customer: I need a halt in my journey. 
 agent: Unfortunately, there is no flights found based on your details. 
 customer: Ok, no issues. Thank you. 
 agent: Thank you.
no_flight