func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long int mod = 1e9 + 7;   const long long int cmod = 998244353;   const long long int N = 2e5 + 5;   const long long int inf = 1e16 + 2;   void solve(long long int ze) {     long long int n, x, t, pr = 0;     cin >> n >> x;     vector<long long int> ans;     map<long long int, long long int> check;     check[0] = 1;     check[x] = 1;     for (long long int i = 1; i < (1LL << n); i++) {       if (!check[i]) {         ans.push_back(pr ^ i);         pr = i;         check[i] = 1;         check[i ^ x] = 1;       }     }     cout << ans.size() <<   n ;     for (auto x : ans) cout << x <<    ;   }   int32_t main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     long long int testcase = 1;     long long int x = 1;     while (testcase--) {       solve(x++);     }     return 0;   }   