#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;
}