#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define int long long
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
template<class T, class U> inline bool chmin(T& a, const U& b) { if (a > b) { a = b; return true; } return false; }
template<class T, class U> inline bool chmax(T& a, const U& b) { if (a < b) { a = b; return true; } return false; }
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template <typename T>
using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
void solve() {
int n;
cin >> n;
vector<int> a(n);
for (int &i : a) cin >> i;
const int N = 2e6 + 1;
bitset<N> bt;
for (int i = 0; i < n; i++) bt[a[i]] = !bt[a[i]];
bitset<N> ans;
for (int i = 0; i < n; i++) {
ans ^= bt << a[i];
bt[a[i]] = !bt[a[i]];
}
int res = 0;
for (int i = 0; i < N; i++) {
if (ans[i]) res ^= i;
}
cout << res;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
