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:       That looks like an interesting book .  
 Person2:It is . It ’ s got pictures of interesting building from all over the world , with brief descriptions of how they were build , their purpose , and so on .  
 Person1:        There are the pymeids . It ’ s easy to see how they got that name ! they don ’ t have smooth sides though .  
 Person2:They don ’ t now , but most of them did originally . There ’ s picture of the pentagon in the United States . It ’ s very distinctive with its five sides .  
 Person1:        Look at that cylindrical office building . I ’ Ve never been seen one that shape before .  
 Person2:Yes . Usually only towers are cylindrical in shape .  
 Person1:        Tv towers are usually thicker at the bottom than at the top . They ’ re not perfectly cylindrical .  
 Person2:This is the world ’ s largest sports stadium . It ’ s a massive oval .  
 Person1:        What sports do they play there ?  
 Person2:It says here that it ’ s mainly used for big football matches and athletics meetings .  
 Person1:        Is that building a perfect cube ?  
 Person2:According to the book , it is . I ’ Ve never seen a building that is a perfect cube . Look at the building . From the air , it looks like a square with a semi-circle attached to each of its four sides . What kind of building is it ?  
 Person1:        Is says here that it ’ s a war memorial . Now , there ’ s a distinctive structure-the stomium in Brussels . See ? It consists of several connected by cylinders . I believe you can go up and down inside it . 

informal