import java.util.*;

public class Run {
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        ArrayList<Integer> C = new ArrayList<>();
        for (int i = 0; i < N; i++) C.add(i+1);
        int M = scan.nextInt();
        int A;
        for (int i = 0; i < M; i++) {
            A = scan.nextInt();
            if (A!=1) {
                C.add(0, C.get(A - 1));
                C.remove(A);
            }
        }
        System.out.println(C.get(0));
    }
}