Definition: You are given a conversation between two people. 'Person1:' and 'Person2:' are used to separate their respective dialogues. You are required to assign a label 'formal' if there is an absence of emotion and a presence of questions anywhere within the conversation. If such pattern is not found assign the label 'informal'.
Input:  Person1:       Can I help you , sir ?  
 Person2:Yes , I've been sitting here for a few minutes . I'm waiting for someone to put gas in my car .  
 Person1:        I'm sorry , sir . But this is the self-service pump .  
 Person2:Self-service ?  
 Person1:        Yes . You must fill up the car yourself .  
 Person2:Are you serious ?  
 Person1:        Yes . Are you traveling here ?  
 Person2:Yes , I'm from Taiwan . I never heard of a gas station where you fill up your own car .  
 Person1:        In America , most gas stations are like this .  
 Person2:Do I really have to do it ? I don't know how .  
 Person1:        Well , since this is your first time , I will do it for you.But next time , if you want a full-service gas station , you should look at the sign .  
 Person2:What sign ?  
 Person1:        Under the sign for the gas station , there will be a smaller sign that says Self-Serve or Full-Service.And some gas stations have both.But if they have both , some pumps will be self-serve and some will be full-serve.You have to look at the signs .  
 Person2:I see . 

informal