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:       We are going to the concert this evening . Will you join us ?  
 Person2:I'm very sorry I can't .  
 Person1:        Why not ?  
 Person2:I've been snowed under with work since my boss was away on business . 

formal