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:       Lisa , I am told you did very well in your exam .  
 Person2:I was the only one who got a strait A in my class .  
 Person1:        Congratulations on your success .  
 Person2:Thank you . 

informal