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:       May I have my bill , please ?  
 Person2:That's $ 20 in all .  
 Person1:        Well , I am afraid you have made a mistake . Would you check it again , please ?  
 Person2:Let me see . I am terribly sorry , sir . That should be $ 18 .  
 Person1:        It doesn't matter . 

informal