#include <iostream>
#include <vector>
#include <bitset>
#include <algorithm>
signed main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);std::cout.tie(nullptr);
int n;
std::cin >> n;
std::vector<int> a(n);
for (int &i : a) std::cin >> i;
std::sort(a.begin(), a.end());
const int N = 1e9 + 1;
std::bitset<N> bt;
for (int i = 0; i < n; i++) bt[a[i]] = !bt[a[i]];
std::bitset<N> ans;
int last = 0;
for (int i = 0; i < n; i++) {
bt <<= (a[i] - last);
ans ^= bt;
last = a[i];
bt[a[i] * 2] = !bt[a[i] * 2];
}
int res = 0;
for (int i = 0; i < N; i++) {
if (ans[i]) res ^= i;
}
std::cout << res;
}
