#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:512000000")
using namespace std;
void solve(__attribute__((unused)) bool);
void precalc();
clock_t start;
int main() {
  start = clock();
  int t = 1;
  cout.sync_with_stdio(0);
  cin.tie(0);
  precalc();
  cout.precision(10);
  cout << fixed;
  int testNum = 1;
  while (t--) {
    solve(true);
  }
  cout.flush();
  return 0;
}
template <typename T>
T binpow(T q, T w, T mod) {
  if (!w) return 1 % mod;
  if (w & 1) return q * 1LL * binpow(q, w - 1, mod) % mod;
  return binpow(q * 1LL * q % mod, w / 2, mod);
}
template <typename T>
T gcd(T q, T w) {
  while (w) {
    q %= w;
    swap(q, w);
  }
  return q;
}
template <typename T>
T lcm(T q, T w) {
  return q / gcd(q, w) * w;
}
template <typename T>
void make_unique(vector<T>& a) {
  sort(a.begin(), a.end());
  a.erase(unique(a.begin(), a.end()), a.end());
}
template <typename T>
void relax_min(T& cur, T val) {
  cur = min(cur, val);
}
template <typename T>
void relax_max(T& cur, T val) {
  cur = max(cur, val);
}
void precalc() {}
const int INF = (int)1e9;
vector<int> get_dp(vector<int> a) {
  vector<int> res(4, -INF);
  if (a.size() == 2) {
    if (a[0] != a[1]) {
      res[1] = res[2] = 1;
    } else if (a[0]) {
      res[3] = 1;
    } else {
      res[0] = 0;
    }
    return res;
  }
  int mid = (int)a.size() / 2;
  auto lef_dp = get_dp(vector<int>(a.begin(), a.begin() + mid));
  auto rig_dp = get_dp(vector<int>(a.begin() + mid, a.end()));
  for (int m1 = 0; m1 < 4; ++m1) {
    for (int m2 = 0; m2 < 4; ++m2) {
      int new_m = (m1 | m2);
      if (lef_dp[m1] < 0 || rig_dp[m2] < 0) {
        continue;
      }
      int new_dp_val = lef_dp[m1] + rig_dp[m2];
      for (int j = 0; j < 2; ++j) {
        if (new_m & (1 << j)) {
          ++new_dp_val;
        }
      }
      if (new_m & 2) {
        ++new_dp_val;
      }
      relax_max(res[new_m], new_dp_val);
    }
  }
  return res;
}
void solve(__attribute__((unused)) bool read) {
  int n, k;
  cin >> n >> k;
  if (k == 0) {
    cout << "0\n";
    return;
  }
  vector<int> a(k);
  vector<int> have(1 << n);
  for (int& x : a) {
    cin >> x;
    --x;
    have[x] = 1;
  }
  auto res = get_dp(have);
  int mx = *max_element(res.begin(), res.end());
  cout << mx + 1 << endl;
}
