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:       I'm here to express my congratulations to you on your birthday . And I wish you many happy returns of the day . Here is a birthday present for you . 
 Person2:Many thanks for your presence . 

informal