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:       Do I have to write the invitation cards ? 
 Person2:No , you don ’ t have to . But I think you ought to . 
 Person1:        Oh , well . If I must , I must . 

formal