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:       Alice , I never knew you had such a lovely voice . You really can sing , can't you ?  
 Person2:Thanks , Mark . I used to be a member of the school choir .  
 Person1:        No wonder you can control your voice so well . You are a professional singer .  
 Person2:Well , you are flattering me . I wouldn't say I am a professional , but I did receive some training at school . My music teacher used to be a professional singer .  
 Person1:        Well , a good teacher makes good students .  
 Person2:You are quite right . 

informal