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:       It's getting late . I'm afraid I have to leave.Thank you for a most wonderful evening . 
 Person2:Don't mention it.Don ' t forget to take your daughter along next time . 
 Person1:        OK . 
Output:
informal