Codeforces Round #793 (Div. 2) 1682 B - AND Sorting Solution

 Problem Link:  https://codeforces.com/contest/1682/problem/B

 Solution in C++: 

///La ilaha illellahu muhammadur rasulullah

///******Bismillahir-Rahmanir-Rahim******///

///Abul Hasnat  Tonmoy

///Department of CSE,23rd batch

///Islamic University,Bangladesh

///**********ALLAH IS ALMIGHTY************///

#include <bits/stdc++.h>

using namespace std;

int main()

{

    int  n,t,i,j,mx,x;

    cin>>t;

    while(t--)

    {

        set<int>s;

        cin>>n;

        for(i=0;i<n;i++)

        {

            cin>>x;

            if(i!=x)

            s.insert(x);

        }

        mx=*s.begin();

        for(auto j:s)

        {

            mx=mx&j;

        }

        cout<<mx<<endl;

    }

}