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 sdf[30] = {4,   22,  27,  58,  85,  94,  121, 166, 202, 265,
               274, 319, 346, 355, 378, 382, 391, 438, 454, 483,
               517, 526, 535, 562, 576, 588, 627, 634, 636, 645};
long long int a[71720], b, c, d, n, m, i, j, k, sum, sumend;
bool cmp(int a, int b) { return a > b; }
int gcd(int a, int b) {
  if (!b) return a;
  return gcd(b, a % b);
}
int gqt(int n) {
  if (!n || n) return 0;
  if (n == 2) return 1;
  for (int i = 3; i <= sqrt(n); i++)
    if (n % i == 0) return 0;
  return 1;
}
int main() {
  cin >> n;
  for (i = 1; i <= n; i++) cin >> a[i];
  sum = a[n];
  sort(a + 1, a + n + 1);
  sumend = a[n];
  cout << (sumend ^ sum) << endl;
  return 0;
}
