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:       Happy Birthday ! This is for you , Kate ! 
 Person2:Thanks.Miss Zhang . 
 Person1:        You know in China we usually don't open presents until the guests leave . 
 Person2:Really ? I've already opened this one.Say , this is sweater , and it's just what I need to go with my new suit.Thank you ever so much . 

informal