#include <bits/stdc++.h>
using namespace std;
const int N=200000+5;
int n,ans;
int a[N];
int main(){
    freopen ("and_sorting.in","r",stdin);
    freopen ("and_sorting.out","w",stdout);
    int T;
    scanf("%d",&T);
    for (int tt=1;tt<=T;tt++){
        scanf("%d",&n);
        ans=(1<<20)-1;
        for (int i=1;i<=n;i++){
            scanf("%d",&a[i]);
            if (a[i]!=i-1){
                ans=ans&a[i];
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}