#include<bits/stdc++.h>
    using namespace std;
    int t, n, p,i;     
    int main() {
        freopen("and_sorting.in", "r", stdin);
        freopen("and_sorting.out", "w", stdout);
        cin >> t;
        while(i <= t) {
            cin >> n; 
            int mi = INT_MAX;
            for(int j = 0; j < n; j ++) {
                cin >> p;
                if(p != j) {
                    mi =mi& p;
                }
            }
            cout << mi << endl;
            i++;
        }
        return 0;
    }