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

    let mut exp = p.iter().sum::<usize>();
    let mut result = 0usize;
    let mut val2score = vec![0usize; n+1];
    for i in 0..n { val2score[p[i]] = i+1; }
    for i in (1..=n).rev() {
        let score = val2score[i];
        if exp >= 2*score {
            result = result.max(exp - 2*score);
        }
        exp -= score;
    }
    println!("{}", result);
}