#include <iostream>
using namespace std;
int main(void) {
// your code goes here
int arr[1000],i;
int n,ans=0;
cin>>n;
for(i=0;i<n;i++)
{
cin>>arr[i];
}
for(i=0;i<n;i++)
{
ans=ans^arr[i];
}
cout<<ans<<endl;
return 0;
}
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