#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <cstdlib>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
using namespace std;
int lonelyinteger(vector < int > a) {
    int res = 0;
    for(int i = 0;i<(int)a.size();i++)
        res ^= a[i];
    return res;
}
int main() {
    int res;
    
    int _a_size;
    cin >> _a_size;
    cin.ignore (std::numeric_limits<std::streamsize>::max(), '\n'); 
    vector<int> _a;
    int _a_item;
    for(int _a_i=0; _a_i<_a_size; _a_i++) {
        cin >> _a_item;
        _a.push_back(_a_item);
    }
    
    res = lonelyinteger(_a);
    cout << res;
    
    return 0;
}

 
import java.io.*;
import java.util.*;

class Bismillah {

  public static void main(String[] args){
    Scanner in = new Scanner(System.in);
	
	
	int n = in.nextInt();
	int[] ai = new int[n];
	int i, j;
	int x = 0;
	boolean state;
	
	
	for (i = 0; i < n; i++) {
	  ai[i] = in.nextInt();
	}
	
	
	for (i = 0; i < n; i++) {
	  state = true;
	  for (j = 0; j < i; j++) {
		if (ai[i] == ai[j]) {
		  j = i; 
		  state = false;
		}
	  }
	  if (state == true) {
	    for (j = i+1; j < n; j++) {
		  if (ai[i] == ai[j]) {
		    j = n; 
		    state = false;
		  }
	    }
		if (state == true) {
		  x = i;		
		  i = n; 		
		}
	  }
	}
	
	
	System.out.println(ai[x]);
  }
}

def lonelyinteger(a):
    a = sorted(a)
    if len(a) < 3:
        return a[0]
    elif a[0] != a[1]:
        return a[0]
    else:
        return lonelyinteger(a[2:])

if __name__ == '__main__':
    a = int(input())
    b = map(int, input().strip().split(" "))
    print(lonelyinteger(b))

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <assert.h>
int lonelyinteger(int a_size, int* a) {
    int res = 0;
    for(int i=0; i<a_size; i++){
        res = res^a[i];
    }
    return res;

}
int main() {
    int res;
    
    int _a_size, _a_i;
    scanf("%d", &_a_size);
    int _a[_a_size];
    for(_a_i = 0; _a_i < _a_size; _a_i++) { 
        int _a_item;
        scanf("%d", &_a_item);
        
        _a[_a_i] = _a_item;
    }
    
    res = lonelyinteger(_a_size, _a);
    printf("%d", res);
    
    return 0;
}