/*#include<iostream>
#include<string>
#include<cctype>
using namespace std;
bool is_digits_only(const string& s)
{
    if(s.empty())
    {
        return false;
    }
    for (char c:s)
    {
        if(!isdigit(c))
        {
            return false;
        }
    }
    return true;
}
int main()
{
    string s1="1234567890";
    string s2="12a34";
    cout<<"Input: "<<s1<<"< Output: "<<(is_digit-only(s1)?"True":"False")<<endl;
    cout<<"Input: "<<s2<<"< Output: "<<(is_digit-only(s2)?"True":"False")<<endl;
}*/
#include<iostream>
using namespace std;
int main()
{
    int n;
    cin>>n;
    int result = 0,x;
    for(int i=0;i<n;++i)
    {
        cin>>x;
        result^=x;
    }
    cout<<result<<endl;
    return 0;
}