#include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int n, k;     cin >> n >> k;     vector<bool> pref(1 << n);     for (int i = 0; i < k; i++) {       int x;       cin >> x;       pref[x - 1] = true;     }     const int oo = -1;     vector<vector<vector<int>>> dp(         4, vector<vector<int>>(n + 1, vector<int>(1 << n, oo)));     for (int i = 0; i < (1 << n); i += 2) {       if (pref[i] && pref[i + 1])         dp[3][1][i] = 1;       else if (pref[i] || pref[i + 1])         dp[1][1][i] = dp[2][1][i] = 1;       else         dp[0][1][i] = 0;     }     for (int i = 2; i <= n; i++)       for (int j = 0; j < (1 << n); j += (1 << i))         for (int p = 0; p < 4; p++)           for (int q = 0; q < 4; q++)             if (dp[p][i - 1][j] != -1 && dp[q][i - 1][j + (1 << (i - 1))] != -1) {               int t = dp[p][i - 1][j] + dp[q][i - 1][j + (1 << (i - 1))];               int upper = ((p & 2) > 0) + ((q & 2) > 0);               int lower = ((p & 1) + (q & 1));               if (upper == 2) {                 t += (lower > 0) + 2;                 dp[3][i][j] = max(dp[3][i][j], t);                 if (lower < 2) dp[2][i][j] = max(dp[2][i][j], t);               } else if (upper == 1) {                 t += (lower > 0) + 1;                 if (lower == 0) {                   dp[2][i][j] = max(dp[2][i][j], t);                   dp[1][i][j] = max(dp[1][i][j], t + 1);                   dp[0][i][j] = max(dp[0][i][j], t + 1);                 }                 if (lower == 1) {                   dp[3][i][j] = max(dp[3][i][j], t + 1);                   dp[2][i][j] = max(dp[2][i][j], t + 1);                   dp[1][i][j] = max(dp[1][i][j], t + 1);                   dp[0][i][j] = max(dp[0][i][j], t + 1);                 }                 if (lower == 2) {                   dp[3][i][j] = max(dp[3][i][j], t + 1);                   dp[2][i][j] = max(dp[2][i][j], t + 1);                   dp[1][i][j] = max(dp[1][i][j], t + 1);                 }               } else if (upper == 0) {                 t += (lower > 0);                 if (lower == 0) dp[0][i][j] = max(dp[0][i][j], t);                 if (lower == 1) {                   dp[1][i][j] = max(dp[1][i][j], t + 1);                   dp[0][i][j] = max(dp[0][i][j], t + 1);                 }                 if (lower == 2) {                   dp[1][i][j] = max(dp[1][i][j], t + 1);                   dp[0][i][j] = max(dp[0][i][j], t + 1);                 }               }             }     int ans = 0;     for (int p = 0; p < 4; p++) ans = max(dp[p][n][0] + (p > 0), ans);     cout << ans <<   n ;     return 0;   }   