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 , ma'am . Can I help you ?  
 Person2:Yes , please . I'd like a gin and tonic .  
 Person1:        Sure , ma'am . Here you are .  
 Person2:Thank you . How much is it ?  
 Person1:        25 yuan .  
 Person2:Here's 30 . Keep the change .  
 Person1:        Thank you very much , ma'am , but we don't take tips in China . 

informal