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:       Hello , Kith , can you and Alice come around this evening ? We prefer your coming .  
 Person2:I think we would be able to make it . What time shall we come ?  
 Person1:        About 7 o'clock .  
 Person2:Shall we bring any thing ? Some wine ?  
 Person1:        No , not really . Just bring yourselves . We would like to your presence . 

informal