#include <bits/stdc++.h>

using i64 = long long;
using PII = std::pair<int, int>;

void solve() {
    int n, a;
    std::cin >> n;
    int ans = (1 << 30) - 1;
    for (int i = 1; i <= n; ++ i) {
        std::cin >> a;
        if (a != i - 1) ans &= a;
    }
    std::cout << ans << '\n';
}

int main() {
    freopen("and_sorting.in", "r", stdin); 
    freopen("and_sorting.out", "w", stdout);
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int t;
    std::cin >> t;
    while (t --) solve();
    return 0;
}