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:       As we know , mobile phones bring people great convenience and shorten the distance among friends and relatives .  
 Person2:It bears a great many of advantages , but also some weak points .  
 Person1:        Is it ? I've never thought of any disadvantages of the mobile phone .  
 Person2:For instance , the mobile phone seriously distracts the attention of people from work and study .  
 Person1:        That's true . Some people pay too much attention to their mobile phones .  
 Person2:Actually , it's not the fault of the mobile phone . But people should have a proper attitude towards it . Mobile phone is a tool serving people , not the fetters restricting them . 

formal