#include<bits/stdc++.h>
using namespace std;
#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define ll long long int
#define fr for(int i=0;i<n;i++)
#define tc int t;  cin >> t;  while(t--)
#define yes cout<<"YES"<<endl
#define no cout<<"NO"<<endl

int main()
{
    fastio;
    int n;
    int x;
    cin>>n;
    int a[n+10];

    fr cin>>a[i];

    sort(a,a+n);



    fr
    {
        if( a[i] != a[i+1] and a[i] != a[i-1])
        {
            x = a[i];
        }
    }

    cout<<x<<endl;

}