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:       Do you know what the BBS is ? 
 Person2:Sure . 
 Person1:        Tell me then . 
 Person2:BBS means Bulletin Board Service . 
 Person1:        Oh , I see , but what's it used for ? 
 Person2:A lot of things ! 
 Person1:        Tell me in details . 
 Person2:Okay . BBS , an online service , offers a wide variety of online games , files , one-on-one chat , message areas , private mail , and participate forums . 
 Person1:        Oh , that's great . I want to try later . 
 Person2:Why not ? 

informal