import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        ArrayList<Integer> cards = new ArrayList<>();
        for (int i = 1; i <= n; i++) {
            cards.add(i);
        }
        for (int i = 0; i < m; i++) {
            int x = sc.nextInt() - 1;
            cards.add(0, cards.remove(x));
        }
        System.out.println(cards.get(0));
    }
}