#[allow(dead_code)]
pub mod uto {
    pub fn read_string() -> String {
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        buf.trim().to_string()
    }

    pub fn drop_line() {
        read_string();
    }

    pub fn read_vec<T>() -> Vec<T>
    where
        T: std::str::FromStr + Copy,
        T::Err: std::fmt::Debug,
    {
        read_string()
            .split_ascii_whitespace()
            .map(|e| e.parse().unwrap())
            .collect::<Vec<_>>()
    }

    pub fn read_double<T>() -> (T, T)
    where
        T: std::str::FromStr + Copy,
        T::Err: std::fmt::Debug,
    {
        let v = read_vec();
        (v[0], v[1])
    }
}

fn main() {
    uto::drop_line();
    let a = uto::read_vec::<usize>();

    let mut score = 0;
    for e in &a {
        if !a.contains(&(e - 1)) {
            score += *e;
        }
    }

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