#![allow(non_snake_case)]
#[allow(unused_imports)]
use proconio::{fastout, input, marker::*};

#[fastout]
fn main() {
    input! {
        N: usize,
        A: [isize; N],
    }

    let mut ans = 0;
    let mut S = {
        let mut s = std::collections::BTreeSet::new();

        for i in 0..N {
            s.insert((A[i], i));
        }

        s
    };

    for i in 0..N {
        if i % 2 == 0 {
            let m = S.pop_last().unwrap().0;
            ans += m;
        } else {
            let m = S.pop_last().unwrap().0;
            ans += -(-m);
        }
    }

    println!("{}", ans);
}