use std::io::*;

fn main() {
    let mut s = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let mut a: Vec<usize> = itr.map(|e| e.parse().unwrap()).collect();
    a.reverse();

    let mut ans: usize = n;

    for i in a {
        if i == ans { ans -= 1; }
    }

    println!("{}", ans);
}