#include<map>
#include<queue>
#include<cmath>
#include<cstdio>
#include<stack>
#include<iostream>
#include<cstring>
#include<algorithm>
#define LL long long
#define inf 0x3f3f3f3f
#define eps 1e-8
#define mod 1000000007
#define ls l,mid,mpt<<1
#define mps mid+1,mp,mpt<<1|1
using namespace std;
int main(){
    LL n,m,k,i,j,cla;
    while(~scanf("%I64d",&cla)){
        while(cla--){
            scanf("%I64d",&n);
            if(n==1){
                scanf("%d",&j);
                printf("%d\n",j);
                continue;
            }
            LL ans=0;
            for(i=0;i<n;++i){
                scanf("%I64d",&k);
            }
            puts("0");
        }
    }
    return 0;
}