#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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