fn main() {
    let stdin = std::io::read_to_string(std::io::stdin()).unwrap();
    let mut stdin = stdin.split_ascii_whitespace();

    let n: usize = stdin.next().unwrap().parse().unwrap();
    let a: Vec<u32> = (0..n)
        .map(|_| stdin.next().unwrap().parse().unwrap())
        .collect();

    println!("{}", output(solve(a)));
}

fn solve(a: Vec<u32>) -> u32 {
    let mut l = 0;
    let mut r = a.len() as u32;
    while l + 1 < r {
        let c = l.midpoint(r);

        let mut prev = 0;
        if a.iter().filter(|&a| *a >= c).all(|a| {
            if prev < *a {
                prev = *a;
                true
            } else {
                false
            }
        }) {
            r = c;
        } else {
            l = c;
        }
    }
    l
}

fn output(ans: u32) -> u32 {
    ans
}