// MagicDark
#include <bits/stdc++.h>
#define debug cerr << "\33[32m[" << __LINE__ << "]\33[m "
#define SZ(x) ((int) x.size() - 1)
#define all(x) x.begin(), x.end()
#define ms(x, y) memset(x, y, sizeof x)
#define F(i, x, y) for (int i = (x); i <= (y); i++)
#define DF(i, x, y) for (int i = (x); i >= (y); i--)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
template <typename T> T& chkmax(T& x, T y) {return x = max(x, y);}
template <typename T> T& chkmin(T& x, T y) {return x = min(x, y);}
template <typename T> T& read(T &x) {
	x = 0; int f = 1; char c = getchar();
	for (; !isdigit(c); c = getchar()) if (c == '-') f = - f;
	for (; isdigit(c); c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
	return x *= f;
}
const int N = 5e5 + 10;
const ll INF = 1e18;
int n, a[N];
ll dp[2];
map <int, vector <int>> mp;
struct BIT {
	int t[N], tim[N], cnt;
	void modify(int x, int y) {
		for (; x <= n; x += x & - x) {
			if (tim[x] != cnt) tim[x] = cnt, t[x] = y;
			else t[x] += y;
		}
	}
	int query(int x) {
		int s = 0;
		for (; x; x -= x & - x)
			if (tim[x] == cnt) s += t[x];
		return s;
	}
	int query(int l, int r) {
		return query(r) - query(l - 1);
	}
} ds, op[2];
ll s1[2][N], s2[2][N], r1[N], r2[N];
int w1[N], w2[N];
signed main() {
	// freopen("sort.in", "r", stdin);
	// freopen("sort.out", "w", stdout);
	read(n);
	F(i, 1, n) {
		mp[- abs(read(a[i]))].push_back(i);
		ds.modify(i, 1);
	}
	dp[1] = INF;
	int res = n;
	for (auto [a, b]: mp) if (a) {
		int A = a;
		ll ndp[2];
		ndp[0] = ndp[1] = INF;
		vector <int> o[2];
		for (int i: b) {
			o[(i & 1) ^ (::a[i] < 0)].push_back(i);
			ds.modify(i, - 1);
		}
		for (int i: b) {
			w1[i] = ds.query(1, i);
			w2[i] = ds.query(i, n);
		}
		F(t, 0, 1) {
			s2[t][o[t].size() + 1] = 0;
			F(i, 1, o[t].size()) {
				s1[t][i] = s1[t][i - 1] + w1[o[t][i - 1]];
			}
			DF(i, o[t].size(), 1) {
				s2[t][i] = s2[t][i + 1] + w2[o[t][i - 1]];
			}
		}
		// in
		F(a, 0, 1)
			F(b, 0, 1)
				F(c, 0, 1)
					F(d, 0, 1)
						if (o[0].size() + (a == 1 && b == 1) + (c == 1 && d == 1) == o[1].size() + (a == 0 && b == 0) + (c == 0 && d == 0)) {
							if (dp[a] != INF && (d ^ a) == (res & 1)) {
								// debug << A << " " << a << " " << b << " " << c << " " << d << endl;
								{
									F(t, 0, 1) op[t].cnt++;
									// op.cnt++;
									for (int t: o[1]) {
										op[1].modify(t, 1);
									}
									int pos = - 1;
									// ll ss = 0;
									auto del = [&] () {
										pos++;
										if (pos <= SZ(o[1])) {
											op[0].modify(o[1][pos], 1);
											op[1].modify(o[1][pos], - 1);
											// pos++;
										}
									};
									if (a) del();
									F(t, 1, o[0].size()) {
										if (pos <= SZ(o[1])) {
											r1[t] = r1[t - 1] + op[0].query(o[0][t - 1], n) + op[1].query(1, o[0][t - 1]);
											// op.modify(o[0][t - 1], 1);
										} else r1[t] = INF;
										del();
									}
								}
								{
									F(t, 0, 1) op[t].cnt++;
									// op.cnt++;
									for (int t: o[1]) {
										op[0].modify(t, 1);
									}
									int pos = SZ(o[1]) + 1;
									// ll ss = 0;
									auto del = [&] () {
										pos--;
										if (pos >= 0) {
											op[1].modify(o[1][pos], 1);
											op[0].modify(o[1][pos], - 1);
											// pos--;
										}
									};
									if (d) del();
									r2[o[0].size() + 1] = 0;
									DF(t, o[0].size(), 1) {
										if (pos >= 0) {
											r2[t] = r2[t + 1] + op[0].query(o[0][t - 1], n) + op[1].query(1, o[0][t - 1]);
											// op.modify(o[0][t - 1], 1);
										} else r2[t] = INF;
										del();
									}
								}
								F(i, 0, o[0].size()) {
									if (a == 0 && b == 0 && i == 0) continue;
									if (c == 0 && d == 0 && i == o[0].size()) continue;
									// debug << "@ " << r1[i] << " " << r2[i + 1] << endl;
									chkmin(ndp[b ^ 1], dp[a] + r1[i] + r2[i + 1] + s1[0][i] + s1[1][i - (a == 0 && b == 0) + (a == 1 && b == 1)] + s2[0][i + 1] + s2[1][i - (a == 0 && b == 0) + (a == 1 && b == 1) + 1]);
								}
							}
						}
		res -= b.size();
		swap(dp, ndp);
		// debug << dp[0] << " " << dp[1] << endl;
		// ll ans = min(dp[0], dp[1]);
		// if (ans == INF) puts("-1");
		// else cout << ans << '\n';
	}
	ll ans = min(dp[0], dp[1]);
	if (ans == INF) puts("-1");
	else cout << ans << '\n';
	return 0;
}
/* why?
*/