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:       I've booked an air ticket to Venice .  
 Person2:How long will you be there ?  
 Person1:        I'd like to stay there for a week .  
 Person2:So you'll have a tour of the famous city .  
 Person1:        Certainly . 

formal