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:       How nice these sunglasses are !  
 Person2:Yes , they are the latest designs . Would you like to try them on ?  
 Person1:        I want to try on this pair .  
 Person2:The round shape pair ?  
 Person1:        That's right .  
 Person2:I think it suits you well .  
 Person1:        I agree , how much ?  
 Person2:120 yuan .  
 Person1:        It's not expensive . OK . I'll take them . 

informal