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:       Excuse me , sir . I wonder if I could exchange the shoes for a larger one .  
 Person2:No problem . May I see your receipt , please ?  
 Person1:        Here you are .  
 Person2:That's right . Now try on this one . It's size 41 . 

informal