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:       You're going to Shanghai tomorrow , are you ? 
 Person2:That's right . Do you think it'll be cold ? 
 Person1:        It might be . You'd better take a heavy sweater with you.The nights are usually quite cold at this time of year . 
 Person2:Do you think I'll need a cotton coat ? 
 Person1:        Not for now , I think , But I believe there'll be rain , so take your raincoat with you . 

formal