#[allow(unused_imports)]
use std::cmp::{max, min};
#[allow(unused_imports)]
use std::collections::{HashMap, HashSet, BTreeSet};

mod util {
    use std::io::stdin;
    use std::str::FromStr;
    use std::fmt::Debug;

    #[allow(dead_code)]
    pub fn line() -> String {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.trim().to_string()
    }

    #[allow(dead_code)]
    pub fn get<T: FromStr>() -> T
    where
        <T as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.trim().parse().unwrap()
    }

    #[allow(dead_code)]
    pub fn gets<T: FromStr>() -> Vec<T>
    where
        <T as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        line.split_whitespace()
            .map(|t| t.parse().unwrap())
            .collect()
    }

    #[allow(dead_code)]
    pub fn get2<T: FromStr, U: FromStr>() -> (T, U)
    where
        <T as FromStr>::Err: Debug,
        <U as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        let mut iter = line.split_whitespace();
        (
            iter.next().unwrap().parse().unwrap(),
            iter.next().unwrap().parse().unwrap(),
        )
    }

    #[allow(dead_code)]
    pub fn get3<S: FromStr, T: FromStr, U: FromStr>() -> (S, T, U)
    where
        <S as FromStr>::Err: Debug,
        <T as FromStr>::Err: Debug,
        <U as FromStr>::Err: Debug,
    {
        let mut line: String = String::new();
        stdin().read_line(&mut line).unwrap();
        let mut iter = line.split_whitespace();
        (
            iter.next().unwrap().parse().unwrap(),
            iter.next().unwrap().parse().unwrap(),
            iter.next().unwrap().parse().unwrap(),
        )
    }
}


#[allow(unused_macros)]
macro_rules! debug {
    ($x: expr) => {
        println!("{}: {:?}", stringify!($x), $x)
    }
}

fn rank(k: usize, buddy: usize, a: &[usize]) -> usize {
    let t = k + buddy;
    let mut l = 0;
    let mut r = a.len() - 1;
    let mut cnt = 0;
    let mut skipped = false;

    while r > l {
        if !skipped && a[l] == buddy {
            l += 1;
            skipped = true;
            continue;
        }
        if !skipped && a[r] == buddy {
            r -= 1;
            skipped = true;
            continue;
        }
        if a[l] + a[r] > t {
            r -= 1;
            l += 1;
            cnt += 1;
        } else {
            l += 1;
        }
    }
    cnt
}

fn main() {
    let (n, m): (usize, usize) = util::get2();
    let k: usize = util::get();
    let mut a: Vec<usize> = (1..n).map(|_| util::get()).collect();

    a.sort();
    let mut scores = a.clone();
    scores.dedup();

    let res = scores.binary_search_by_key(&(n - m + 1), |&buddy| n - rank(k, buddy, &a));
    match res {
        Ok(i) => {
            println!("{}", scores[i]);
        }
        Err(i) => {
            if i == scores.len() {
                println!("-1");
            } else {
                println!("{}", scores[i]);
            }
        }
    }
}