#include <iostream>

int main()
{
    using namespace std;
    size_t T;
    cin >> T;

    while (T--) {

        size_t N;
        cin >> N;

        int value, result;
        result = 0;

        for (size_t i = 0; i < N; ++i) {

            cin >> value;

            if (((i + 1) & 1) && ((N - i) & 1))
                result ^= value;
        }

        cout << (result^0) << endl;
    }

    return 0;
}