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;
inline void GetN(int &num) {
  char in = getchar();
  while (in < '0' || in > '9') in = getchar();
  num = in - '0';
  while (in = getchar(), in >= '0' && in <= '9') num *= 10, num += in - '0';
}
inline void GetS(char *s) {
  memset(s, 0, sizeof(s));
  char in = getchar();
  while ((in < 'A' || in > 'Z') && (in < 'a' || in > 'z')) in = getchar();
  int len = 0;
  s[len] = in;
  while (in = getchar(), (in >= 'A' && in <= 'Z') || (in >= 'a' && in <= 'z'))
    s[++len] = in;
}
int n, i, x, ans = 1, mx, a[100];
bool mrk[20];
int main() {
  memset(mrk, false, sizeof(mrk));
  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%d", a + i);
    mrk[a[i]] = true;
    if (a[i] > mx) mx = a[i];
  }
  ans = mx;
  ans = ans ^ a[n - 1];
  cout << ans << endl;
}
