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 Paul Walker. 
 agent: Hello, How can I serve you? 
 customer: Due to sudden changes in weather, my football tournament has been cancelled. Can you please help me with cancellation? 
 agent: Sure, Please wait a minute. 
 customer: Sure. 
 agent: Your ticket has been cancelled. Thank you for opting us. 
 customer: Thank you for your valuable information.
cancel