#include <iostream>
#include <algorithm>
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];
sort(x, x + n);
long long k, y;
k = 1;
y = x[0];
for (int i = 1; i < n; i++) {
if (x[i] == y)
k++;
else {
if (k % 2 != 0) {
cout << y;
return 0;
}
else {
k = 1;
y = x[i];
}
}
}
cout << x[n - 1];
delete []x;
return 0;
}
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