#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define pb push_back
#define F first
#define S second
#define in insert
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N = 1e6 + 123;
const int P = 320;
const int mod = 1e9 + 7;
ll n, m, k;
ll a[N];
ll t[N * 4];
void salemkhan() {
cin >> n;
for(int i = 1; i <= n; i++) {
cin >> a[i];
}
ll s = a[1] + a[1];
for(int i = 1; i <= n; i++) {
for(int j = i; j <= n; j++) {
if(i == j && i == 1) continue;
s ^= a[i] + a[j];
}
}
cout << s;
}
// 28 37 48 49 55 56 57 58 67 9
// 9 + 1 +
int main() {
//freopen("knight.in", "r", stdin);
//freopen("knight.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll tt = 1;
//cin >> tt;
while(tt--) {
salemkhan();
}
}
