#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

long long inversion_number(vector<int> &A){
    int N = A.size();
    vector<int> B = A;
    sort(B.begin(), B.end());
    map<int, int> mp;
    for (int i = 0; i < N; i++) mp[B[i]] = i + 1;
    for (int i = 0; i < N; i++) A[i] = mp[A[i]];
    long long ans = 0;
    vector<int> BIT(N + 1, 0);
    for (int i = 0; i < N; i++){
        ans += i; int j;
        j = A[i]; while (j > 0){ ans -= BIT[j]; j -= j & -j; }
        j = A[i]; while (j <= N){ BIT[j]++; j += j & -j; }
    }
    return ans;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N; cin >> N;
    vector<int> A(N);
    rep(i,N) cin >> A[i];
    cout << (inversion_number(A) % 2 == 0 ? +1 : -1) << endl;
}