import java.util.*;

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