Instructions: 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: Study hard , otherwise you'll fail .
Person2:Yes , Mum .
Person1: Don't render me lip-service , you'd better stay at home tonight .
Person2:But it's Sunday , isn't it ?
Output:
formal