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:       Is there a train leaving for Philadelphia ?  
 Person2:Yeah . There's an express that leaves in twenty minutes .  
 Person1:        May I buy a ticket here at the station ?  
 Person2:Sure .  
 Person1:        Where ?  
 Person2:Go to window number eleven .  
 Person1:        Thanks . 

informal