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 ’ ll sing you a song .  
 Person2:Yes , sing a song . But don ’ t sing a sad song .  
 Person1:        Most of my songs are sad , sorry .  
 Person2:Well , please sing one that ’ s not sad .  
 Person1:        OK , I ’ ll sing San Francisco then . 

informal