#include <bits/extc++.h>

int main() {
    using namespace std;
    unsigned long N;
    cin >> N;
    vector<unsigned long> P(N), invP(N);
    for(auto&& p : P){
        cin >> p;
        --p;
    }
    for(unsigned long i{}; i < N; ++i)invP[P[i]] = i;
    unsigned long res{};
    const auto swp{[&res, &P, &invP](unsigned long i, unsigned long j){
        if(i == j)return;
        res ^= 1;
        swap(P[i], P[j]);
        swap(invP[P[i]], invP[P[j]]);
    }};
    for(unsigned long i{}; i < N; ++i)swp(i, invP[i]);
    if(res)cout << '-';
    cout << 1 << endl;
    return 0;
}