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:       Could I change these pounds for dollars , please ?  
 Person2:Do you want small bills or large ?  
 Person1:        It doesn't matter .  
 Person2:Do you want anything else ?  
 Person1:        Yes , I'd like to know the exchange rate for yen . 

formal