#include <iostream>
#include <vector>
 
using namespace std;
 
typedef long long ll;
 
ll merge_count(vector<int> &a) {
    int n = a.size();
    if (n <= 1) { return 0; }
 
    ll cnt = 0;
    vector<int> b(a.begin(), a.begin()+n/2);
    vector<int> c(a.begin()+n/2, a.end());
 
    cnt += merge_count(b);
    cnt += merge_count(c);
 
    int ai = 0, bi = 0, ci = 0;
 
    while (ai < n) {
        if ( bi < b.size() && (ci == c.size() || b[bi] <= c[ci]) ) {
            a[ai++] = b[bi++];
        } else {
            cnt += n / 2 - bi;
            a[ai++] = c[ci++];
        }
    }
    return cnt;
}
 
int main() {
    int n; cin >> n;
    vector<int> a(n);
 
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
 
    cout << (merge_count(a)%2 ? -1 : 1)<< endl;
    return 0;
}