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:       Can you assure the quality of this air conditioner ?  
 Person2:Yes , ma'ma . There'll be no problem with the quality .  
 Person1:        What if there's something wrong with it ?  
 Person2:You don't have to worry about it . We have a one year warranty .  
 Person1:        Are you sure ?  
 Person2:Sure . We have a good after-sale service . Your satisfaction is guaranteed . 

formal