func_code_string: #include <bits/stdc++.h>   using namespace std;   const int INF = 1e9 + 10;   const int SZ = 2e5 + 10;   const int mod = 1e9 + 7;   long long read() {     long long n = 0;     char a = getchar();     bool flag = 0;     while (a >  9  || a <  0 ) {       if (a ==  - ) flag = 1;       a = getchar();     }     while (a <=  9  && a >=  0 ) {       n = n * 10 + a -  0 , a = getchar();     }     if (flag) n = -n;     return n;   }   int a[SZ], b[SZ], p[SZ], pri[SZ], vis[SZ];   int main() {     int n = read(), x = read();     for (int i = 1, j = 0; i < (1 << n); i++) {       if (i == x)         continue;       else {         if (x < (1 << n)) {           int ii = x ^ i;           if (ii < i) a[++a[0]] = i;         } else           a[++a[0]] = i;       }     }     for (int i = a[0]; i >= 2; i--) a[i] ^= a[i - 1];     printf( %d n , a[0]);     for (int i = 1; i <= a[0]; i++) printf( %d  , a[i]);     return 0;   }   