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>
int Fl, Pn, SI = 100;
char mch = ' ', ch, Bf[21];
template <typename t>
void in(t& a) {
  a = 0;
  ch = getchar();
  Fl = 1;
  while ((ch < '0') || (ch > '9')) Fl = (ch == '-') ? -Fl : Fl, ch = getchar();
  while ((ch >= '0') && (ch <= '9')) a = a * 10 + ch - '0', ch = getchar();
  a *= Fl;
}
template <typename t>
void out(t a) {
  if (a < 0) putchar('-'), a = -a;
  if (a == 0) putchar('0');
  while (a) Bf[++Pn] = a % 10 + '0', a /= 10;
  while (Pn) putchar(Bf[Pn]), --Pn;
  putchar(mch);
}
template <typename t, typename... ARGS>
void in(t& a, ARGS&... args) {
  in(a);
  in(args...);
}
template <typename t, typename... ARGS>
void out(t a, ARGS... args) {
  out(a);
  out(args...);
}
using namespace std;
int n, x, mx;
int main() {
  in(n);
  for (register int i = 1; i <= n; i++) in(x), mx = max(mx, x);
  out(x ^ mx);
  return 0;
}
