超级玛丽

import java.util.Scanner;


public class Main {
    static int n,m;
    static int[] a;
    static int ans=0;
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        n = scanner.nextInt();
        m = scanner.nextInt();
        a = new int[m];
        for (int i = 0; i < m; i++) {
            a[i]=scanner.nextInt();
        }
        f(1,a,0);
        System.out.println(ans);
    }
    private static void f(int i, int[] a, int j) {
        if (j>n) {
            return;
        }
        if (j==n) {
            ans++;
            return ;
        }
        for (int j2 = 0; j2 < m; j2++) {
            if (j==a[j2]) {
                return ;
            }
    }
        f(i+2, a, j=i+2);
        f(i+1, a, j=i+1);
    }


}