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:       Lily , do you know Lizzy ? 
 Person2:Lizzy who ? 
 Person1:        Lizzy smith . 
 Person2:Of course I do . 
 Person1:        Then , Do you know her younger sister ? 
 Person2:You mean Mary ? 
 Person1:        Yes . 
 Person2:Sure . I know her elder sister Sue and younger sister Mary . 
 Person1:        Oh , not bad . Then do you know her mother ? 
 Person2:Yes , certainly . I know her mother and father , and brother and sisters , too . 
 Person1:        That sounds terrific . 
 Person2:Why do you ask me these questions ? 
 Person1:        I just want to visit the family some day . 

informal