#include <bits/stdc++.h>   inline long long read() {     long long x = 0, f = 1;     char c = getchar();     for (; c >  9  || c <  0 ; c = getchar()) {       if (c ==  - ) f = -1;     }     for (; c >=  0  && c <=  9 ; c = getchar()) {       x = x * 10 + c -  0 ;     }     return x * f;   }   int dp[18][(1 << 18)][2][2];   bool fan[200005];   inline void work() {     int n = read(), k = read();     for (int i = 1; i <= k; i++) {       int x = read();       fan[x] = 1;     }     memset(dp, -0x3f, sizeof dp);     for (int i = 1; i <= n; i++) {       for (int j = 1; j <= (1 << n); j += (1 << i)) {         if (i == 1) {           dp[i][j][fan[j]][fan[j + 1]] = (fan[j] | fan[j + 1]);           dp[i][j][fan[j + 1]][fan[j]] = (fan[j] | fan[j + 1]);         } else {           for (int x1 = 0; x1 < 2; x1++) {             for (int x2 = 0; x2 < 2; x2++) {               for (int y1 = 0; y1 < 2; y1++) {                 for (int y2 = 0; y2 < 2; y2++) {                   int tmp =                       dp[i - 1][j][x1][y1] + dp[i - 1][j + (1 << i - 1)][x2][y2];                   if (x1 | x2) tmp++;                   if (y1 | y2) tmp++;                   dp[i][j][x1][x2] = std::max(dp[i][j][x1][x2], tmp + (x2 | y1));                   dp[i][j][x1][x2] = std::max(dp[i][j][x1][x2], tmp + (x2 | y2));                   dp[i][j][x1][y1] = std::max(dp[i][j][x1][y1], tmp + (y1 | x2));                   dp[i][j][x1][y2] = std::max(dp[i][j][x1][y2], tmp + (y2 | x2));                   dp[i][j][x2][x1] = std::max(dp[i][j][x2][x1], tmp + (x1 | y1));                   dp[i][j][x2][x1] = std::max(dp[i][j][x2][x1], tmp + (x1 | y2));                   dp[i][j][x2][y1] = std::max(dp[i][j][x2][y1], tmp + (y1 | x1));                   dp[i][j][x2][y2] = std::max(dp[i][j][x2][y2], tmp + (y2 | x1));                 }               }             }           }         }       }     }     int ans = -0x3f3f3f3f;     ans = std::max(ans, dp[n][1][1][1] + 1);     ans = std::max(ans, dp[n][1][0][1] + 1);     ans = std::max(ans, dp[n][1][1][0] + 1);     ans = std::max(ans, dp[n][1][0][0]);     printf( %d n , ans);   }   int main() {     work();     return 0;   }   