#include <bits/stdc++.h>

#define ctz __builtin_ctz

using namespace std;

using ull = unsigned long long;

const int LG = 64;
const int S0 = 13;
const int S1 = 7;
const int S2 = 17;

const int N = 1e5;

int n;
int a[N + 5], pos[N + 5], rem[N + 5];
ull v[LG];
vector<pair<ull, bool>> equ;
vector<int> fr;
ull ans;
ull xorshift(ull &x) { return x ^= x << S0, x ^= x >> S1, x ^= x << S2; }

int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) scanf("%d", a + i), pos[a[i]] = i;
  for (int i = n; i; --i) rem[i] = pos[i] - 1, pos[a[pos[i]] = a[i]] = pos[i];
  for (int i = 0; i < LG; ++i) v[i] = 1ull << i;
  for (int i = 1; i <= n; ++i) {
    for (int k = LG - 1; k >= S0; --k) v[k] ^= v[k - S0];
    for (int k = 0; k < LG - S1; ++k) v[k] ^= v[k + S1];
    for (int k = LG - 1; k >= S2; --k) v[k] ^= v[k - S2];
    for (int k = ctz(i) - 1; k >= 0; --k) equ.emplace_back(v[k], rem[i] >> k & 1);
  }
  for (int i = 0; i < LG; ++i) {
    int pivot = i;
    for (; pivot < equ.size() && (~equ[pivot].first >> i & 1); ++pivot);
    if (pivot >= equ.size()) { fr.push_back(i); continue; }
    if (pivot > i) swap(equ[i], equ[pivot]);
    for (int j = 0; j < equ.size(); ++j)
      if (i != j && (equ[j].first >> i & 1))
        equ[j].first ^= equ[i].first, equ[j].second ^= equ[i].second;
  }
  for (int s = 0; s < 1 << fr.size(); ++s) {
    ans = 0;
    for (int i = 0; i < fr.size(); ++i) ans ^= (ull)(s >> i & 1) << fr[i];
    for (int i = 0; i < LG && i < equ.size(); ++i)
      if (equ[i].first >> i & 1) {
        ans ^= (ull)equ[i].second << i;
        for (int j = i + 1; j < LG; ++j)
          if (equ[i].first >> j & 1) ans ^= (ans >> j & 1) << i;
      }
    ull x = ans; bool flag = 1;
    for (int i = 1; i <= n; ++i)
      if (xorshift(x) % i != rem[i]) { flag = 0; break; }
    if (flag) break;
  }
  printf("%llu\n", ans);
}