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:       Let's meet tonight at the Thai restaurant at about 5 .  
 Person2:Fine , I'll take a taxi .  
 Person1:        Why don't you walk ? It's only about 20 minutes walking and it's a nice evening .  
 Person2:Never thought about it , I sure you are right . It's quite a short walk .  
 Person1:        Ha-ha , see you then . 

informal