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:       I'm sorry , but I can't find the book you lent me . I guess I have lost it . 
 Person2:Don't worry about it . 
 Person1:        I really feel bad about it . Let me buy you a new one . 
 Person2:No . Don't be silly . I wouldn't dream of letting you do that . 

informal