#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define N 600005
#define pb push_back
#define ff first
#define ss second
#define all(x) x.begin(),x.end()
#define sz(s) (int)s.size()
ll T, n, a[N], t, answer, galan;
map <int,int> vis, vip;
vector <int> s;
int main () {
cin >> n;
for(int i = 1;i <= n; i++){
cin >> a[i];
vis[a[i]]++;
}
for(int i=1;i<=n;i++) {
if(!vis[a[i]]) continue;
if(vis[a[i]] == 1) {
s.pb(a[i]);
continue;
}
if(vis[a[i]] % 2 == 0) galan = (galan ^ (a[i] * 2));
else {
vip[a[i]] = 1;
s.pb(a[i]);
}
vis[a[i]] = 0;
}
for(int i = 0; i < sz(s); i++) {
for(int j = i; j < sz(s); j++) {
if(vip[s[i]]) {
vip[s[i]]--;
continue;
}
galan = (galan ^ (s[i] + s[j]));
}
}
cout << galan << '\n';
}
