#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
#include "algo/debug.hpp"
#else
#define debug(...) ((void)0)
#endif

#include <atcoder/fenwicktree>
int main() {
  constexpr char endl = '\n';
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int n; cin >> n;
  vector<int> a(n);
  for(auto&x: a) cin >> x, x--;
  atcoder::fenwick_tree<int> fw(n);
  int tt = n * (n - 1) / 2;
  for(int i = 0; i < n; i++) {
    tt -= fw.sum(0, a[i]);
    fw.add(a[i], 1);
  }
  cout << (tt & 1 ? -1 : 1) << endl;
}