#include<cstdio>
using namespace std;
int n,i,x,T,ans,j;
int main()
{
    scanf("%d",&T);
    while (T--)
      {
          scanf("%d",&n);
          for (i=1;i<=n;i++)
            scanf("%d",&x);
          if (n==1) printf("%d\n",x);
          else printf("%d\n",0);
      }
    return 0;
}