DO YOU EXPECT ME TO FIND THIS OUT?

WHAT BASE AND/XOR LANGUAGE INCLUDES string?

DON'T BYTE OF MORE THAN YOU CAN CHEW

YOU CAN ONLY DISTORT THE LARGEST OF MATHEMATICS SO FAR

SAYING "ABRACADABRA" WITHOUT A MAGIC AND WON'T DO YOU ANY GOOD

THE LAST STACK RUPTURES. ALL DIE. OH, THE EMBARRASSMENT!

I HAVE NO ARRAY AND I MUST SCREAM

ELEMENTS MAY NOT BE STORED IN WEST HYPERSPACE

Input

The first line of input data contains a single integer n (1 ≤ n ≤ 10).

The second line of input data contains n space-separated integers ai (1 ≤ ai ≤ 11).

Output

Output a single integer.

Example

Input

4
2 5 3 1


Output

4
#include <bits/stdc++.h>
using namespace std;
int gcd(int a, int b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
int lcm(int a, int b) { return (b / gcd(a, b)) * a; }
void print() {}
void pLine() { cout << endl; }
template <typename T, typename... arg>
void print(T x, arg... ar) {
  cout << x;
  print(ar...);
}
const double PI = acos(-1);
const double eps = numeric_limits<double>::epsilon();
void bubbleSort(vector<int> arr, int n) {
  bool swapped = true;
  int j = 0;
  int tmp;
  while (swapped) {
    swapped = false;
    j++;
    for (int i = 0; i < n - j; i++) {
      if (arr[i] > arr[i + 1]) {
        tmp = arr[i];
        arr[i] = arr[i + 1];
        arr[i + 1] = tmp;
        swapped = true;
      }
    }
  }
}
void sol() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (auto &i : a) cin >> i;
  int mx = *max_element(a.begin(), a.end());
  int last = a[n - 1];
  cout << (last ^ mx);
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  sol();
  return 0;
}
