#include<stdio.h>
int main()
{
int t;
scanf("%d", &t);
while(t--)
{
long long int a,n,s=0,i;
scanf("%lld", &n);
for(i=0;i<n;i++)
{
scanf("%lld", &a);
s^=a;
}
printf("%lld\n",s);
}
return 0;
}
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