func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     int t;     cin >> t;     while (t--) {       bool f = false;       set<int> v1;       int n, ans = -1;       cin >> n;       int a[n];       for (long long i = 0; i < n; i++) {         cin >> a[i];         v1.insert(a[i]);       }       for (int i = 1; i <= 1024; i++) {         long long count = 0;         for (int j = 0; j < n; j++) {           int m = a[j] ^ i;           v1.insert(a[j] ^ i);           if (v1.size() > n) {             count++;             v1.erase(v1.find(m));             break;           }         }         if (count == 0) {           ans = i;           break;         }       }       cout << ans << endl;     }     return 0;   }   