func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     if (false) {       freopen( input.txt ,  r , stdin);       freopen( output.txt ,  w , stdout);     }     int n;     cin >> n;     vector<int> v(n + 1, -1);     int xx = 1048576;     long long sum = 0;     for (int i = n; i > 0; i--) {       if (v[i] >= 0) {         continue;       }       while (xx / 2 > i) {         xx /= 2;       }       int a = i ^ (xx - 1);       v[i] = a;       v[a] = i;       sum += (a + i) * 2;     }     if (v[0] < 0) {       v[0] = 0;     }     cout << sum << endl;     for (int i = 0; i <= n; i++) {       if (i > 0) {         cout <<    ;       }       cout << v[i];     }     cout << endl;     if (false) {       fclose(stdin);       fclose(stdout);     }     return 0;   }   