func_code_string: #include <bits/stdc++.h>   using namespace std;   using ll = long long;   const int maxn = 1e6 + 6;   int a[maxn];   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     int n;     cin >> n;     int pt = 0;     if (n & 1) {       for (int i = 2; i <= n; i += 2) {         a[pt++] = i;       }       for (int i = n - 1; i >= 2; i -= 2) {         a[pt++] = i;       }       for (int i = 1; i <= n; i += 2) {         a[pt++] = i;       }       for (int i = n - 2; i >= 1; i -= 2) {         a[pt++] = i;       }       a[pt++] = n;     } else {       for (int i = 1; i <= n; i += 2) {         a[pt++] = i;       }       for (int i = n - 1; i >= 1; i -= 2) {         a[pt++] = i;       }       for (int i = 2; i <= n; i += 2) {         a[pt++] = i;       }       for (int i = n - 2; i >= 2; i -= 2) {         a[pt++] = i;       }       a[pt++] = n;     }     for (int i = 0; i < pt; i++) {       cout << a[i] <<    ;     }     cout <<   n ;   }   