#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int MAXN=1000,INF=0x3f3f3f3f;
int T,n,ans;
int main(){
    scanf("%d",&T);
    for(;T;T--){
        scanf("%d",&n);ans=0;
        for(int i=1,t;i<=n;i++){
            scanf("%d",&t);ans^=t;
        }
        if(n==1)printf("%d\n",ans);
        else printf("%d\n",0); 
    }
    return 0;
}