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:       Congratulations , Vivian . You won the grand prize , again .  
 Person2:Isn't it just great ! I just knew I'd win !  
 Person1:        You did ? How ? Did you wear red underwear again this year ?  
 Person2:Not only that !  
 Person1:        Tell me ! Tell me ! What's your secret ? !  
 Person2:OK , OK . I'll whisper it to you , but you have to promise not to tell anyone !  
 Person1:        What ? ! You did that ? ? ! ! ! 

informal