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:       I think the biggest environment problem in my country is air pollution .  
 Person2:Yes , I agree . The air here is much more polluted than in my country .  
 Person1:        That's because your country is more agricultural and has much less industry .  
 Person2:Yeah , you are right .  
 Person1:        We have reduced emission of air pollutants in recent years , but cars are still a major source of them . Factories have become cleaner as stricter environment pollution laws have been introduced .  
 Person2:The problem is now on a truly global scale . I don't believe that any single country can do anything about it .  
 Person1:        I think you're right . An international response to this problem is needed . 

informal