// >>> TEMPLATES
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define int ll
#define double ld
#define rep(i,n) for (int i = 0; i < (int)(n); i++)
#define rep1(i,n) for (int i = 1; i <= (int)(n); i++)
#define repR(i,n) for (int i = (int)(n)-1; i >= 0; i--)
#define rep1R(i,n) for (int i = (int)(n); i >= 1; i--)
#define loop(i,a,B) for (int i = a; i B; i++)
#define loopR(i,a,B) for (int i = a; i B; i--)
#define all(x) (x).begin(), (x).end()
#define allR(x) (x).rbegin(), (x).rend()
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fst first
#define snd second
#define INF (numeric_limits<int>::max()/2-1)
#ifdef LOCAL
#include "debug.hpp"
#define dump(...) cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] ", dump_impl(#__VA_ARGS__, __VA_ARGS__)
#define say(x) cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] " << x << endl
#define debug if (1)
#else
#define dump(...) (void)(0)
#define say(x) (void)(0)
#define debug if (0)
#endif
template <class T> using pque_max = priority_queue<T>;
template <class T> using pque_min = priority_queue<T, vector<T>, greater<T> >;
template <class T, class = typename T::iterator, class = typename enable_if<!is_same<T, string>::value>::type>
ostream& operator<<(ostream& os, T const& v) { bool f = true; for (auto const& x : v) os << (f ? "" : " ") << x, f = false; return os; }
template <class T, class = typename T::iterator, class = typename enable_if<!is_same<T, string>::value>::type>
istream& operator>>(istream& is, T &v) { for (auto& x : v) is >> x; return is; }
template <class T, class S> istream& operator>>(istream& is, pair<T,S>& p) { return is >> p.first >> p.second; }
struct IOSetup { IOSetup() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } iosetup;
template <class F> struct FixPoint : private F {
    constexpr FixPoint(F&& f) : F(forward<F>(f)) {}
    template <class... T> constexpr auto operator()(T&&... x) const { return F::operator()(*this, forward<T>(x)...); }
};
struct MakeFixPoint {
    template <class F> constexpr auto operator|(F&& f) const { return FixPoint<F>(forward<F>(f)); }
};
#define MFP MakeFixPoint()|
#define def(name, ...) auto name = MFP [&](auto &&name, __VA_ARGS__)
template <class T, size_t d> struct vec_impl {
    using type = vector<typename vec_impl<T,d-1>::type>;
    template <class... U> static type make_v(size_t n, U&&... x) { return type(n, vec_impl<T,d-1>::make_v(forward<U>(x)...)); }
};
template <class T> struct vec_impl<T,0> { using type = T; static type make_v(T const& x = {}) { return x; } };
template <class T, size_t d = 1> using vec = typename vec_impl<T,d>::type;
template <class T, size_t d = 1, class... Args> auto make_v(Args&&... args) { return vec_impl<T,d>::make_v(forward<Args>(args)...); }
template <class T> void quit(T const& x) { cout << x << endl; exit(0); }
template <class T> constexpr bool chmin(T& x, T const& y) { if (x > y) { x = y; return true; } return false; }
template <class T> constexpr bool chmax(T& x, T const& y) { if (x < y) { x = y; return true; } return false; }
template <class It> constexpr auto sumof(It b, It e) { return accumulate(b,e,typename iterator_traits<It>::value_type{}); }
template <class T> int sz(T const& x) { return x.size(); }
// <<<
// >>> RLE for vector
template <class T, class F>
vector<tuple<T,int,int> > RLE(vector<T> const& v, F f) {
    if (v.empty()) return {};
    vector<tuple<T,int,int> > ret;
    int ii = -1, n = v.size();
    rep (i,n) if (i == n-1 || f(v[i]) != f(v[i+1])) {
        ret.emplace_back(v[i],ii+1,i+1);
        ii = i;
    }
    return ret;
}
// <<<
// >>> RLE for vector
template <class T>
vector<pair<T,int> > RLE(vector<T> const& v) {
    if (v.empty()) return {};
    vector<pair<T,int> > ret;
    int ii = -1, n = v.size();
    rep (i,n) if (i == n-1 || v[i] != v[i+1]) {
        ret.emplace_back(v[i],i-ii);
        ii = i;
    }
    return ret;
}
// <<<

int32_t main() {
    int n; cin >> n;
    auto a = make_v<int,2>(2,n); cin >> a;

    int mi = INF;
    rep (s,1<<n) {
        vector<pair<int,int> > v[2];
        rep (i,n) {
            int x = s>>i&1, y = i&1;
            v[x^y].eb(a[x][i],i);
        }
        sort(all(v[0]));
        sort(all(v[1]));
        pair<int,int> err = mp(-1,-1);
        vector<pair<int,int> > w(n,err);
        rep (i,sz(v[0])) if (2*i < n) w[2*i] = v[0][i];
        rep (i,sz(v[1])) if (2*i+1 < n) w[2*i+1] = v[1][i];
        auto check = [&]() {
            if (count(all(w),err)) return false;
            rep (i,n-1) if (w[i].fst > w[i+1].fst) return false;
            return true;
        };
        if (!check()) continue;
        int cnt = 0;
        rep (i,n) rep (j,n) if (i < j && w[i].snd > w[j].snd) cnt++;
        chmin(mi, cnt);
    }

    if (mi == INF) mi = -1;
    cout << mi << endl;
}


Measured memory_bytes: 256