#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;
}
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