use std::collections::VecDeque;

fn main() {
    let mut input = String::new();
    std::io::Read::read_to_string(&mut std::io::stdin(), &mut input).ok();
    let input: Vec<u64> = input
        .split_whitespace()
        .map(|n| n.parse().unwrap())
        .collect();

    let mut cards: VecDeque<_> = (1..=input[0]).collect();

    for &i in &input[2..] {
        let removed = cards.remove(usize::try_from(i).unwrap() - 1).unwrap();
        cards.push_front(removed);
    }

    println!("{}", cards.pop_front().unwrap());
}