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:       Hello and welcome . How may I be of service ?  
 Person2:Hello . I want to buy some RIB , is it OK to use US dollars ?  
 Person1:        Yes , of course . What's the amount you'd like to change ?  
 Person2:I think 250 dollars should be sufficient .  
 Person1:        Please fill out this exchange form and I'll need to see your passport . Don't forget to sign your name at the bottom .  
 Person2:Oh , right , of course . Here you go .  
 Person1:        Here is your RIB , the exchange form and receipt and your passport . Please check the amount .  
 Person2:It's correct . Is there any way I can change it back before I leave the country ?  
 Person1:        Yes , that can be done here . Just make sure you keep the exchange form and the receipt and you can come back at the end of your stay and we'll be only to happy to change it back into foreign currency .  
 Person2:That's wonderful news , thanks for all your help . 

informal