#include <bits/stdc++.h>
using namespace std;
typedef long long i64;
const int maxn = 500000;
int n;
struct item {
	int v, id, s;
	bool operator<(const item& b) const {
		if (v == b.v) {
			if (s == b.s) return id < b.id;
			return s < b.s;
		}
		return v > b.v;
	}
} p[maxn + 5];
i64 f[maxn + 5][2][2];
struct BIT {
	int t[maxn + 5];
	void modify(int x, int v) {
		for (; x <= n; x += x & (-x)) t[x] += v;
	}
	int query(int x) {
		int rs = 0;
		for (; x; x -= x & (-x)) rs += t[x];
		return rs;
	}
} t1, t2;
int l0[maxn + 5], l1[maxn + 5];
i64 v[maxn + 5];
bool vis[maxn + 5];
inline void upd(i64& x, i64 y) { x = min(x, y); }
int main() {
	scanf("%d", &n);
	for (int i = 1, a; i <= n; i++) {
		scanf("%d", &a);
		if (a < 0) p[i] = {-a, i, ~i & 1};
		else p[i] = {a, i, i & 1};
	}
	sort(p + 1, p + n + 1);
	for (int i = 1; i <= n; i++) 
	memset(f, 63, sizeof(f));
	f[0][0][n & 1] = 0;
	for (int i = 1; i <= n; i++) t2.modify(i, 1);
	int c = 1;
	for (int i = 1, j; i <= n; i = j, c++) {
		int m;
		for (m = i; m <= n && p[m].v == p[i].v && !p[m].s; m++) ;
		for (j = m; j <= n && p[j].v == p[i].v; j++) ;
		for (int k = i; k < j; k++) t2.modify(p[k].id, -1);
		for (int x = 0; x < 2; x++)
			for (int y = 0; y < 2; y++) {
				i64 o = f[c - 1][x][y];
				if (o > 1E12) continue;
				l0[0] = i - 1, l1[0] = m - 1; 
				for (int k = 1, s = x; k <= j - i; k++, s ^= 1) {
					l0[k] = l0[k - 1], l1[k] = l1[k - 1];
					int nw = s ? ++l1[k] : ++l0[k];
					if (l0[k] >= m || l1[k] >= j) v[k] = 1E12; 
					else {
						t1.modify(p[nw].id, 1);
						vis[nw] = 1;
						v[k] = v[k - 1] + k - t1.query(p[nw].id) + t2.query(p[nw].id);
					}
				}
				for (int k = i; k < j; k++)
					if (!vis[k]) t1.modify(p[k].id, 1), vis[k] = 1;
				upd(f[c][(x + j - i) & 1][y], o + v[j - i]);
				i64 V = 0;
				for (int k = j - i, L0 = m, L1 = j, s = y; k; k--, s ^= 1) {
					int nw = s ? --L1 : --L0;
					if (L0 < i || L1 < m) V = 1E12;
					else {
						V += k - t1.query(p[nw].id) + n + 1 - j - t2.query(p[nw].id);
						t1.modify(p[nw].id, -1);
						vis[nw] = 0;
					}
					if (l0[k - 1] < L0 && l1[k - 1] < L1) upd(f[c][(x + k - 1) & 1][(y + j - i - k + 1) & 1], o + v[k - 1] + V);
				}
				for (int k = i; k < j; k++)
					if (vis[k]) t1.modify(p[k].id, -1), vis[k] = 0;
			}
	}
	i64 ans = 1E12;
	for (int x = 0; x < 2; x++)
		for (int y = 0; y < 2; y++) upd(ans, f[c - 1][x][y]);
	printf("%lld", ans == 1E12 ? -1 : ans);
}