1 #include<iostream>
 2 #include<cstring> 
 3 #include<cstdio>
 4 #define ll __int64
 5 using namespace std;
 6 int t;
 7 int n;
 8 ll exm;
 9 int main()
10 {
11   int t;
12   scanf("%d",&t);
13   for(int i=1;i<=t;i++)
14   {
15       scanf("%d",&n);
16       for(int j=1;j<=n;j++)
17         scanf("%I64d",&exm);
18       if(n==1)
19        printf("%I64d\n",exm);
20        else
21       cout<<"0"<<endl;
22   } 
23     return 0;
24 }