#include<iotsream>
#include<vector>
using namespace std ;
int findsingleElement(){
    int n;
    cin>>n;
    vector<int>arr(n);
    for (int i=0; i<n; i++)
    {
        cin>>arr[i];
    }
    int result = 0;
    for (int num ; arr)
    {
        result^=num;
    }
    return result;
}
int main()
{
    cout<< findsingleElement()<<endl;
    return 0;
}