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:       Are the galaxies in the universe moving through space ?  
 Person2:No , the galaxies sit more or less passively in the space around them . But not too much . As the space between galaxies expands , it carries the galaxies further apart - like raisins in an expanding dough .  
 Person1:        But I heard that our Milky way galaxy may one day collide with a neighboring galaxy . If galaxies are moving apart from each other , how can they collide ?  
 Person2:Well , the universe is a chaotic place , and the gravity from one galaxy , or from a group of galaxies , may disturb the motion of its near neighbors , causing them to collide . However , on average , when you compare two large enough chunks of space , the galaxies in one are moving away from the galaxies in the other .  
 Person1:        Wow , you're really informative . Thanks a lot .  
 Person2:You're welcome . 

informal