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:       Say , Anna , what are you doing tonight ? Would you like to go out ? 
 Person2:Oh , sorry , I can't . I'm going to work late tonight . I have to finish this report . 
 Person1:        Well , how about tomorrow night ? Are you doing anything then ? 
 Person2:No , I'm not . What are you planning to do ? 
 Person1:        I'm going to see a musical . Would you like to come ? 
 Person2:Sure , I'd love to ! But let me pay for the tickets this time . It's my turn . 
 Person1:        All right ! Thanks ! 

informal