function sansaXor(arr) {

/*if array length is odd xor the elements only at the even indexes as the other elements will appear even no. of times

and a number xored with itself is 0.*/

if(arr.length%2!=0){

var res=0;

for(var i=0; i<arr.length; i=i+2){

res= res^arr[i];

}

return res;

}

//if array length is even all elements will appear even no. of times hence the result will be zero.

else if(arr.length%2==0){

return 0;

}

}

function main() {

var t = parseInt(readLine());

for(var a0 = 0; a0 < t; a0++){

var n = parseInt(readLine());

arr = readLine().split(' ');

arr = arr.map(Number);

var result = sansaXor(arr);

process.stdout.write("" + result + "\n");

}

}