func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       int n;       cin >> n;       int a[n + 1];       int b[2 * n + 1];       int temp[2 * n + 1];       for (int i = 1; i <= 2 * n; i++) temp[i] = 0;       bool con1 = false, con2 = false;       for (int i = 1; i <= n; i++) {         cin >> a[i];         if (a[i] == 1) con1 = true;         if (a[i] == 2 * n) con2 = true;         temp[a[i]] = 1;       }       if (con1 == false or con2 == true)         cout <<  -1  << endl;       else {         int check = 0;         for (int i = 1; i <= n; i++) {           b[2 * i - 1] = a[i];           int j;           for (j = a[i] + 1; j <= 2 * n; j++) {             if (temp[j] == 0) {               temp[j] = 1;               b[2 * i] = j;               break;             }           }           if (j == 2 * n + 1) {             check = -1;           }         }         if (check != -1) {           for (int i = 1; i <= 2 * n; i++) cout << b[i] <<    ;           cout << endl;         } else           cout <<  -1  << endl;       }     }     return 0;   }   