import java.util.LinkedList;
import java.util.Scanner;
public class Main{
	public static void main(String args[])throws Exception{
		Scanner sc=new Scanner(System.in);
		int n,m,are[];
		String ss[]=sc.nextLine().split(" ");
		n=Integer.parseInt(ss[0]);
		m=Integer.parseInt(ss[1]);
		LinkedList<Integer>queue=new LinkedList<Integer>();
		for(int i=1;i<=n;i++){
			queue.offerLast(i);
		}
		for(int i=0;i<m;i++){
			int temp=sc.nextInt()-1;
			queue.offerFirst(queue.remove(temp));
		}sc.close();
		System.out.println(queue.getFirst());
	}
}