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:       What kind of document is an invoice ?  
 Person2:It's a document from the seller to the buyer . It contains full particulars of the goods sold , such as quantity , quality , price , forwarding particulars , and terms of payment .  
 Person1:        How many kinds of foreign invoices are there ?  
 Person2:Four . They are Loco invoice , FOB invoice , CIF invoice and Franco invoice .  
 Person1:        What does the price in different kinds of invoices include ?  
 Person2:By Loco invoice , the price includes only the cost of goods at the warehouse of the seller . By FOB invoice , the price includes the cost before the cargo is delivered . By CIF invoice , the price includes all the expenses of cost freight and insurance . The price in Franco invoice includes all expenses to destination .  
 Person1:        Oh , I see . 

formal