#include <bits/stdc++.h>
using namespace std;

#define INF (int)1e9
#define PI 3.1415926535897932384626433832795
#define mod 1000000007
#define yes cout << "YES" << endl 
#define no cout << "NO" << endl 
#define pb push_back
#define l_b lower_bound
#define u_b upper_bound
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define _fastio  ios_base:: sync_with_stdio(false); cin.tie(0); cout.tie(0);

typedef long long ll;
typedef unsigned long long ull;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<string, string> pss;
typedef map<int, int> mii;
typedef unordered_map<int, int> umap_ii;
typedef unordered_map<string, int> umap_si;


/**
 * Limits in C++ for reference
 * _____________________________________________________________________________________
 * |Sr| Macro Name | Description                     | Value
 * |No|____________|_________________________________|__________________________________
 * |1.| ULLONG_MAX | Maximum value unsigned long long| 18,446,744,073,709,551,615 (10^20)
 * |2.| LLONG_MAX  | Maximum value long long         | 9,223,372,036,854,775,807 (10^19)
 * |3.| LLONG_MIN  | Minimum value long long         |-9,223,372,036,854,775,808 -1*(10^19)
 * |4.| INT_MAX    | Maximum value int               | 2,147,483,647 (10^10)
 * |5.| INT_MIN    | Minimum value int               |-2,147,483,648 (10^10)
*/

void solve()
{
    // Do your thing here :)
    ll n;
    cin >> n;
    vl a(n);
    for(int i=0; i<n; i++) cin >> a[i];

    sort(all(a));
    ll ans=0;
    for(int i=0; i<n-1; i+=2) {

        if(a[i]!=a[i+1]) {
            ans = a[i];
            break;
        }
    }

    if(ans==0) {
        cout << a[n-1] << endl;
    }
    else {
        cout << ans << endl;
    }
}


int main()
{

    _fastio;
    solve();
}