func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       int n, flag = 0;       cin >> n;       vector<int> v(n);       for (int i = 0; i < n; i++) {         cin >> v[i];       }       sort(v.begin(), v.end());       if (v[0] == 0) {         vector<int> v1(n);         for (int k = 1; k < 2000; k++) {           for (int i = 0; i < n; i++) {             v1[i] = (v[i] ^ k);           }           sort(v1.begin(), v1.end());           if (v1 == v) {             cout << k << endl;             flag++;             break;           }         }       } else {         vector<int> v1(n);         for (int k = 1; k < 2000; k++) {           for (int i = 0; i < n; i++) {             v1[i] = (v[i] ^ k);           }           sort(v1.begin(), v1.end());           if (v1 == v) {             cout << k << endl;             flag++;             break;           }         }       }       if (flag == 0) {         cout <<  -1  << endl;       }     }   }   