#include<bits/stdc++.h>
using namespace std;
#define ll long long int 
int main()
{
    ll n;
    cin>>n;
   vector<ll>v(n);
    ll mx=0;
    for(int i=0;i<n;i++)
    {
        cin>>v[i];
        mx=(mx^v[i]);
    }
    cout<<mx<<endl;
}