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 n, a[11], maxx, lost;
inline int qread() {
  int x = 0, f = 1;
  int c = getchar();
  while (c < '0' || c > '9') {
    if (c == '-') f = -1;
    c = getchar();
  }
  while (c >= '0' && c <= '9') {
    x = (x << 1) + (x << 3) + (c ^ 48);
    c = getchar();
  }
  return x * f;
}
inline void qwrite(register int x) {
  if (x < 0) {
    putchar('-');
    x = -x;
    qwrite(x);
  } else {
    if (x > 9) {
      qwrite(x / 10);
    }
    putchar(x % 10 + '0');
  }
}
int main() {
  n = qread();
  for (int i = 1; i <= n; i++) {
    a[i] = qread();
  }
  maxx = a[n];
  sort(a + 1, a + n + 1);
  lost = a[n];
  lost ^= maxx;
  qwrite(lost);
  return 0;
}
