func_code_string: #include <bits/stdc++.h>   using namespace std;   int ans1 = 0, ans2 = 0;   int main(void) {     int t, i, j;     cin >> t;     while (t--) {       int n, mx = INT_MIN, ans = 0, sz;       cin >> n;       int a[n];       set<int> s;       for (i = 0; i < n; i++) {         cin >> a[i];         mx = max(mx, a[i]);         s.insert(a[i]);       }       for (i = 12; i >= 0; i--) {         if (((1 << i) & mx) != 0) break;       }       mx = (1 << (i + 1));       for (i = 1; i <= mx; i++) {         map<int, int> mp;         sz = 0;         for (j = 0; j < n; j++) {           if ((s.count(a[j] ^ i) > 0) && (mp[a[j] ^ i] == 0)) {             sz++;             mp[a[j] ^ i]++;           }         }         if (sz == s.size()) ans = 1;         if (ans == 1) break;       }       if (ans == 0)         cout << -1 << endl;       else         cout << i << endl;     }   }   