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:       Hi , Mark ! Long time no see !  
 Person2:Hi , Alex !  
 Person1:        Where have you been ?  
 Person2:I just got back from London .  
 Person1:        How was your flight ?  
 Person2:It was OK . There was a lot of turbulence , though .  
 Person1:        That ’ s too bad . How long was the flight ?  
 Person2:It was 10 hours .  
 Person1:        Did you have a layover ?  
 Person2:Yes , in Paris , France .  
 Person1:        Did you buy anything in the duty-free stores ?  
 Person2:Yes . I bought two boxed of chocolate – one for me and one for you !  
 Person1:        Oh , you didn ’ t have to ...  
 Person2:It was nothing . 

informal