Instructions: 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: Show us our itineraries , please .
Person2:We'll first go to Mount Tai , then we'll go to Sichuan by air , after that we'll be leaving for Tibet .
Person1: How long will the trip take ?
Person2:At least 20 days .
Output:
formal