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 four o'clock already . I hate to leave , but I think I must .  
 Person2:Can you stay a little longer ?  
 Person1:        I'm sorry , but I can't . 

informal