package card_shuffle;

import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;

public class CardShuffle {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);

		int N = sc.nextInt();
		int M = sc.nextInt();
		int[] A = new int[M];
		List<Integer> cardList = new LinkedList<Integer>();

		for(int cardNum = 1; cardNum <= N; cardNum++) {
			cardList.add(cardNum);
		}

		for(int i = 0; i < M; i++) {
			A[i] = sc.nextInt();
		}

		List<Integer> shuffledCard = new LinkedList<>(cardList);
		for(int a: A) {
			shuffledCard.add(0, shuffledCard.remove(a-1));
		}

		System.out.println(shuffledCard.get(0));
	}

}