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 , Tom . How do you find the dinner of yesterday ? 
 Person2:Very good . That may be the most delicious food I have ever eaten . 
 Person1:        It's nice of you to say so . 
 Person2:I really appreciate you for having invited me . 
 Person1:        Don't mention it . You know , we ’ re old friends . 
 Person2:Anyway , I owe you one . Are you free tonight ? 
 Person1:        Yes . Why ? 
 Person2:I want to invite you to enjoy the food I cook . 
 Person1:        That ’ s great . I'd love to . 

informal