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