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:       How much is the postage for this postcard to China ?  
 Person2:How would you like to send it ?  
 Person1:        By airmail .  
 Person2:Sixty cents please .  
 Person1:        Here you are .  
 Person2:Please write down the zip code in the mailing address .  
 Person1:        Oh , one more thing , I want to send the card by registered mail too .  
 Person2:OK . please give me twenty cents .  
 Person1:        Here it is . and thank you very much .  
 Person2:You're welcome . 

informal