#include<stdio.h>
#include<string.h>
int main()
{
    int n;
    int N;
    int num[2000],ans;
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
    {
        scanf("%d", &N);
        for (int j = 1; j <= N; j++)
            scanf("%d", &num[j]);
        if (N >= 2)
            printf("0\n");
        else
            printf("%d\n", num[1]);
    }
    return 0;
}