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 ?  
 Person2:Yes . I'd like to borrow these books .  
 Person1:        Just a second . I'll see if I can find them for you .  
 Person2:Thanks .  
 Person1:        Here you are . You must return them within a month .  
 Person2:What happens if I'm not finished with them in a month ?  
 Person1:        You can come in and renew them unless someone else has reserved them .  
 Person2:OK . Thank you very much for your trouble .  
 Person1:        No trouble at all . So long . 

informal