#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define xx first #define yy second #define pb push_back #define mp make_pair #define LL long long #define inf INT_MAX/3 #define mod 1000000007ll #define PI acos(-1.0) #define linf (1ll<<60)-1 #define FOR(I,A,B) for(int I = (A); I < (B); ++I) #define REP(I,N) FOR(I,0,N) #define ALL(A) ((A).begin(), (A).end()) #define set0(ar) memset(ar,0,sizeof ar) #define vsort(v) sort(v.begin(),v.end()) #define setinf(ar) memset(ar,126,sizeof ar) //cout << fixed << setprecision(20) << p << endl; template inline T bigmod(T p,T e,T M){ LL ret = 1; for(; e > 0; e >>= 1){ if(e & 1) ret = (ret * p) % M; p = (p * p) % M; } return (T)ret; } template inline T gcd(T a,T b){if(b==0)return a;return gcd(b,a%b);} template inline T modinverse(T a,T M){return bigmod(a,M-2,M);} int ar[1001]; int main() { // ios_base::sync_with_stdio(0); cin.tie(0); int T; cin >> T; while(T--){ int n; cin >> n; int res = 0; REP(i, n){ int x; cin >> x; res ^= x; } if(n > 1) res = 0; cout << res << endl; } }