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>
template <class T>
int getbit(T s, int i) {
  return (s >> i) & 1;
}
template <class T>
T onbit(T s, int i) {
  return s | (T(1) << i);
}
template <class T>
T offbit(T s, int i) {
  return s & (~(T(1) << i));
}
template <class T>
int cntbit(T s) {
  return __builtin_popcount(s);
}
template <class T>
T gcd(T a, T b) {
  T r;
  while (b != 0) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
template <class T>
T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}
using namespace std;
const int MAXN = 2e5 + 100;
const int MOD = 1e9 + 7;
const double eps = 1e-12;
const long long INF = 1e16;
inline string toStr(long long x) {
  string tmp = "";
  do tmp = char(x % 10 + '0') + tmp;
  while (x /= 10);
  return tmp;
}
inline long long toInt(string s) {
  long long res = 0;
  for (auto x : s) res = res * 10 + x - '0';
  return res;
}
int main() {
  int n, x, mmax = 0;
  cin >> n;
  for (int i = 0, _a = (n); i < _a; ++i) cin >> x, mmax = max(mmax, x);
  cout << (mmax ^ x);
}
