func_code_string: #include <bits/stdc++.h>   using namespace std;   const int INF = 0x3f3f3f3f;   int a[205], b[105];   set<int> st;   int n;   void solve() {     cin >> n;     for (int i = 1; i <= n; i++) cin >> b[i];     st.clear();     for (int i = 1; i <= 2 * n; i++) st.insert(i);     for (int i = 1; i <= n; i++) {       st.erase(b[i]);     }     if (st.size() != n) {       cout << -1 << endl;       return;     }     for (int i = 1; i <= n; i++) {       a[2 * i - 1] = b[i];     }     for (int i = 2; i <= 2 * n; i += 2) {       auto tmp = st.upper_bound(a[i - 1]);       if (tmp == st.end()) {         cout << -1 << endl;         return;       }       a[i] = *tmp;       st.erase(tmp);     }     for (int i = 1; i <= 2 * n; i++) {       cout << a[i] <<    ;     }     cout << endl;   }   int main() {     ios::sync_with_stdio(false);     int t;     cin >> t;     while (t--) {       solve();     }     return 0;   }   