fn main() {
    let mut xx = String::new();
    std::io::Read::read_to_string(&mut std::io::stdin(), &mut xx).ok();
    let xx: Vec<u64> = xx.split_whitespace().skip(1).flat_map(str::parse).collect();

    let score = xx.iter().filter(|&&n| !xx.contains(&(n - 1))).sum::<u64>();

    println!("{score}");
}