B.cpp

// #pragma GCC optimize("Ofast,unroll-loops")
// #pragma GCC target("avx,avx2,fma")

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ull unsigned long long
#define dd double
#define ld long double
#define sl(n) scanf("%lld", &n)
#define si(n) scanf("%d", &n)
#define sd(n) scanf("%lf", &n)
#define pll pair <ll, ll>
#define pii pair <int, int>
#define mp make_pair
#define pb push_back
#define all(v) v.begin(), v.end()
#define inf (1LL << 61)
#define loop(i, start, stop, inc) for(ll i = start; i <= stop; i += inc)
#define for1(i, stop) for(ll i = 1; i <= stop; ++i)
#define for0(i, stop) for(ll i = 0; i < stop; ++i)
#define rep1(i, start) for(ll i = start; i >= 1; --i)
#define rep0(i, start) for(ll i = (start-1); i >= 0; --i)
#define ms(n, i) memset(n, i, sizeof(n))
#define casep(n) printf("Case %lld:", ++n)
#define pn printf("\n")
#define pf printf
#define EL '\n'
#define fastio std::ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);

// === Debug macro starts here ===
#ifndef ONLINE_JUDGE
#define DEBUG
#define SYS_COL system("COLOR")
#endif

int recur_depth = 0;
#ifdef DEBUG
#define dbg(x) {++recur_depth; auto x_=x; --recur_depth; SYS_COL; cerr<<string(recur_depth, '\t')<<"\e[91m"<<__func__<<":"<<__LINE__<<"\t"<<#x<<" = "<<x_<<"\e[39m"<<endl;}
#else
#define dbg(x)
#endif
template<typename Ostream, typename Cont>
typename enable_if<is_same<Ostream,ostream>::value, Ostream&>::type operator<<(Ostream& os,  const Cont& v){
	os<<"[";
	for(auto& x:v){os<<x<<", ";}
	return os<<"]";
}
template<typename Ostream, typename ...Ts>
Ostream& operator<<(Ostream& os,  const pair<Ts...>& p){
	return os<<"{"<<p.first<<", "<<p.second<<"}";
}
// === Debug macro ends here ===

#define ff first
#define ss second

const ll sz = 4e5 + 10;
ll ara[sz];

ll calc(vector <int> &v, ll p, ll l, ll r)
{
    ll lft = lower_bound(all(v), l-v[p]) - v.begin();
    ll rgt = upper_bound(all(v), r-v[p]) - v.begin();

    ll tot = rgt-lft;
    if(p >= lft && p < rgt) tot--;
    return tot;
}

int main()
{
    fastio;

    ll n; cin >> n;
    for1(i, n) cin >> ara[i];

    ll ans = 0;

    for(ll b = 0; b <= 30; b++) {
        ll lim = (1LL << (b+1));
        vector <int> v;

        for1(i, n) v.pb(ara[i] % lim);
        sort(all(v));

        ll start = (1LL << b), stop = lim-1, tot = 0;

        for(ll i = 0; i < v.size(); i++) {
            tot += calc(v, i, start, stop);
            tot += calc(v, i, (1LL<<(b+1)) | start, (1LL<<(b+1)) | stop);
        }
        tot /= 2;
        //dbg(mp(cnt[b], tot));
        if(tot & 1) ans ^= (1LL << b);
    }

    cout << ans << EL;

    return 0;
}