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:       So how long have you know Jack ?  
 Person2:We go way back.We ' Ve known each other since we were toddlers .  
 Person1:        Really ? You guys must be really tight .  
 Person2:Yeah , We're buddy-buddy still .  
 Person1:        He seems sincere , and trustworthy .  
 Person2:Well , he is , but he can be conniving at times .  
 Person1:        What do you mean ?  
 Person2:Well , I know that he would never stab me in the back.But I've seen him double cross other people .  
 Person1:        Oh , my ! Really ? I never thought he would be like that .  
 Person2:Don't get me wrong , I'm not saying he's like that all the time .  
 Person1:        So , can I trust him or what ?  
 Person2:Well , I think you should decide for yourself .  
 Person1:        But I need someone that I can count on for this job .  
 Person2:Okay , Okay.You can trust him . I was just trying to give you a hard time .  
 Person1:        Come on you're confusing me.Give it to me straight .  
 Person2:Actually , he's the most dependable person I know , and he would never turn on anyone . 

informal