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;
#pragma comment(linker, "/STACK:102400000,102400000")
long long mul(long long a, long long b) { return (a * b) % (1000000007); }
long long add(long long a, long long b) { return (a + b) % (1000000007); }
long long sub(long long a, long long b) {
  return ((a - b) % (1000000007) + (1000000007)) % (1000000007);
}
void upd(long long &a, long long b) {
  a = (a % (1000000007) + b % (1000000007)) % (1000000007);
}
int read() {
  int x = 0, f = 1;
  char ch = getchar();
  while (!isdigit(ch)) {
    if (ch == '-') f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = x * 10 + ch - '0';
    ch = getchar();
  }
  return x * f;
}
int a[100000];
int main() {
  int n = read();
  for (int i = 1; i <= n; i++) cin >> a[i];
  int p = *max_element(a + 1, a + 1 + n);
  cout << (p ^ a[n]) << endl;
  return 0;
}
