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:       We must set 1000 dollars aside each month .  
 Person2:Why ?  
 Person1:        We are going to buy our own house .  
 Person2:Really ? Congratulations . 

informal