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 val2idx = vec![n; n+1];
    for i in 0..n {
        val2idx[a[i]] = i+1;
    }
    let mut result = 0usize;
    let mut exp = a.iter().sum::<usize>();
    for i in (1..=n).rev() {
        let score = val2idx[i];
        if exp > 2*score {
            result = result.max(exp - 2*score);
        }
        exp -= score;
    }
    println!("{}", result);
}