#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
using namespace std;
#define LL long long

int t;
int n;
LL a;

int main()
{
    scanf("%d", &t);
    for(int tm = 1; tm <= t; tm++)
    {
        scanf("%d", &n);
        for(int i = 0; i < n; i++) scanf("%I64d", &a);
        if(n == 1) printf("%I64d\n", a);
        else printf("0\n");
    }
    return 0;
}