#include <iostream>
using namespace std;
int main() {
long long n, *x;
cin >> n;
x = new long long[n];
for (int i = 0; i < n; i++)
cin >> x[i];
long res = 0;
for (int i = 0; i < n; i++)
res ^= x[i];
cout << res;
delete []x;
return 0;
}
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