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:       Good . There is the information desk . How do we get to seventieth street , please ?  
 Person2:The northern line is what you want .  
 Person1:        How much is it ?  
 Person2:It ’ s two yuan .  
 Person1:        Which way do we go for the northern line ?  
 Person2:Just go through the number eight to ticket barrier over there . A train will be in directly .  
 Person1:        I appreciate it , thank you .  
 Person2:That ’ s all right . 

informal