#include <bits/stdc++.h>
using namespace std;

#define FAST ios_base::sync_with_stdio(false);cin.tie(NULL);
using ll = long long;

int main() {
  FAST;
  
  int n, i, x;
  cin >> n;

  vector<int> a(n);
  for (i = 0; i < n; ++i) cin >> a[i];

  x = 0;
  for (i = 0; i < n; ++i) x ^= a[i];

  cout << x << "\n";

  return 0;
}