#include <iostream>
#include <fstream>

using namespace std;
ifstream fin("clasic.in");
ofstream fout("clasic.out");

int main()
{
    int T, N, x, ok, s;
    clasic c;
    fin >> T >> N;
    while (T) {
        s = 0;
        for (int i = 1; i <= N; i++) {
            fin >> c.val;
            ok = 0;
            for (unsigned int j = 0; j <= v.size(); j++)
                if (v[j].val == c.val) {
                    v[j].apar++;
                    ok = 1;
                }
            if (ok == 0) {
                c.apar = 1;
                v.push_back(c);
            }
        }
        int s = 0;
        for (unsigned int i = 0; i < v.size(); i++)
            if (v[i].apar % 2 == 1)
                s = s ^ v[i].val;
        fout << s << '\n';
        v.clear();
        T--;
    }

     int T, N, x, s;
    fin >> T;
    while (T) {
        s = 0;
        fin >> N;
        for (int i = 1; i <= N; i++) {
            fin >> x;
            s = s ^ x;
        }
        fout << s << '\n';
        T--;
    }
}