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:       Your knowledge of English is really surprising .  
 Person2:Oh , it's nothing to speak of .  
 Person1:        No , seriously . I'm impressed .  
 Person2:Thank you . I appreciate the compliment . 

informal