fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let mut a = a.trim().split_whitespace()
        .map(|x| x.parse().unwrap()).collect::<Vec<isize>>();
    a.sort();

    let mut ans = a[0];
    for i in 1..n {
        if a[i] - a[i - 1] != 1 { ans += a[i]; }
    };

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