#include <bits/stdc++.h>
using namespace std;
#define ll long long
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, k;
    cin >> n >> k;
    vector<bool> branch(n + 1, false);
    for (int i = 0; i < k; i++) {
        int r;
        cin >> r;
        branch[r] = true;
    }
    ll ans = 0;
    for (int i = 1; i <= n; i++) {
        if (branch[i]) {
            ans = 2 * ans + 2;
        } else {
            ans++;
        }
    }
    cout << ans << '\n';

    return 0;
}