mod p1468 {
use std::collections::BTreeSet;

fn gather(v: Vec<String>) -> BTreeSet<String> {
    v.into_iter().fold(BTreeSet::new(), |mut acc, s| {
        acc.insert(s);
        acc
    })
}

pub fn solve(begin: Vec<String>, after: Vec<String>) -> String {
    let begin_set = gather(begin);
    let after_set = gather(after);
    let sub = &begin_set ^ &after_set;
    if sub.is_empty() {
        begin_set
    } else {
        sub
    }.iter().collect::<Vec<_>>()[0].to_owned()
}
}
struct Input {
    num: usize,
    begin: Vec<String>,
    after: Vec<String>,
}

impl Input {
    fn readline(len: usize) ->  Vec<String> {
        use std::io::{self, BufRead};

        let stdin = io::stdin();
        let lines = stdin.lock().lines().map(|l| l.unwrap().to_string());
        lines.take(len).collect()
    }

    fn accept(len: usize) -> Self {
        let lines = Self::readline(len);
        let num = lines[0].parse::<usize>().unwrap();
        let begin = lines[1].split(" ").map(|s| s.to_string()).collect::<Vec<_>>();
        let after = lines[2].split(" ").map(|s| s.to_string()).collect::<Vec<_>>();
        Self {
            num,
            begin,
            after,
        }
    }
}

fn main() {
    let args = Input::accept(3);
    let result = p1468::solve(args.begin, args.after);
    println!("{}", result);
}