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:       The summer vacation is coming . Have you any plans ? 
 Person2:I haven't made up my mind . Maybe I will go to the US . What about you ? 
 Person1:        I am going on a hiking trip . It's good exercise as well as fun . 
 Person2:I think so . 
 Person1:        So why not come and join us ? Lee will come as well . 
 Person2:That's great . I will go hiking with you . 

informal