#include<cstdio>
#include<iostream>
using namespace std;
int main()
{
    int t;
    int n;
    int i,j;
    int a[1005];
    int num;
    scanf("%d",&t);
    while(t--)
    {
        num=0;
        scanf("%d",&n);
        for(i=0;i<n;i++)
            {
                scanf("%d",&a[i]);
                num=num^a[i];
            }
        if(n%2==0) printf("0\n");
        else printf("%d\n",num);
    }
}