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'.

Ex Input:
Person1: There will be another sandstorm here tomorrow .
Person2:It's the fourth one this year . Isn't it horrible .
Person1: Yes . We should plant more trees and grass to stop the sand from spreading .
Person2:It may take many years for the trees to grow . I hope people will stop cutting down trees .
Person1: But we need the wood .
Person2:But we can't destroy our forests to get the wood .

Ex Output:
informal

Ex Input:
Person1: I'm tired .
Person2:Okay , let's call it a day .

Ex Output:
informal

Ex Input:
Person1: Where is the bus ?
Person2:I think it's running late .
Person1: It should've been here 30 minutes ago .
Person2:It should be coming soon .
Person1: It better , because I'm already late for work .
Person2:I can't stand riding the bus .
Person1: Me too , it's so unreliable .
Person2:That is true .
Person1: It's also horrible having to be at a bus stop in any kind of weather .
Person2:Exactly.That ' s the worst part .
Person1: I think it's time we started driving .
Person2:Yes , I agree .

Ex Output:
informal