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:       It's very nice of you to invite me . 
 Person2:I'm very glad you could come , Mr . Liu . Will you take a seat at the head of the table ? It's an informal dinner , please don't stand on ceremony ... Mr . Liu , would you like to have some chicken ? 
 Person1:        Thank you . This is my first time to come to a Chinese restaurant . Could you tell me the different features of Chinese food ? 
 Person2:Generally speaking , Cantonese food is a bit light ; Shanghai food is rather oily ; and Hunan dishes are very spicy , having a strong and hot taste . 
 Person1:        Chinese dishes are exquisitely prepared , delicious , and very palatable . They are very good in colour , flavour , and taste . 
 Person2:Mr . Liu , would you care for another helping ? 
 Person1:        No more , thank you . I'm quite full . 
 Person2:Did you enjoy the meal ? 
 Person1:        It's the most delicious dinner I've had for a long time . It's such a rich dinner . 
 Person2:I'm so glad you like it . 
 Person1:        Thank you very much for your hospitality . 

informal