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:       Do you mind if we call on you this evening ?  
 Person2:Of course not , we'd be happy if you could come.What time will you be able to come ?  
 Person1:        How about seven o'clock ?  
 Person2:Fine.We ' ll be expecting you . 

informal