#include<iostream>
using namespace std;

int main()
{
    int t;
    cin >> t;
    while (t--) {
        int res = 0;
        int n,t;
        cin >> n;
        cin >> t;
        if (n == 1) 
            cout << t << endl;
        else 
            cout << 0 << endl;
        n--;
        while (n--) {
            cin >> t;
        }
    }
    return 0;
}