#include <bitset>
#include <iostream>
#include <vector>

using namespace std;
using Line = bitset<2000 * 2000 + 1>;
int main()
{
    int N;
    cin >> N;
    Line l = 0;
    l[0] = 1;
    for (int i = 0; i < N; i++)
    {
        int a;
        cin >> a;
        l ^= l << a;
    }
    int ans = 0;
    for (int i = 0; i < (int)l.size(); i++)
    {
        if (l[i])
            ans ^= i;
    }
    cout << ans << endl;
}