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:       Hello , is that Cathy speaking ?  
 Person2:Yes , is that you , Allen ?  
 Person1:        Yes , how are you doing ?  
 Person2:Not bad .  
 Person1:        Say I've got two tickets for the concert this evening.Would you like to come with me ?  
 Person2:Sure.Thank you very much .  
 Person1:        Then I ' ll pick you up at six thirty.OK ?  
 Person2:Ok , see you .  
 Person1:        See you . 

informal