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:       We thought you might like to participate in our rehearsal .  
 Person2:I ’ m afraid I ’ m already booked up for next Sunday . But thank you just the same .  
 Person1:        That ’ s a pity . We can arrange another time hopefully . 

informal