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 a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut cnts = vec![0usize; 36];
    for &v in a.iter() {
        cnts[v] += 1;
    }
    let mut result = 0usize;
    for i in 1..36 {
        if cnts[i-1] == 0 {
            result += cnts[i] * i;
        }
    }
    println!("{}", result);
}