#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];
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;
}
bool vis[maxn + 5];
inline void upd(i64& x, i64 y) { x = min(x, y); }
int v[maxn + 5];
i64 v2[maxn + 5];
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++) modify(i, 1);
	int c = 1;
	for (int i = 1, j; p[i].v; 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++) ;
		int len = j - i, len0 = m - i, len1 = j - m;
		for (int k = i; k < j; k++) modify(p[k].id, -1);
		for (int k = i; k < j; k++) v[k] = query(p[k].id);
		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;
				int sta = 0;
				if (~(x ^ y ^ len) & 1) {
					if (len & 1) {
						if (abs(len0 - len1) > 1) continue;
						if ((x && len1 == len0 + 1) || (!x && len0 == len1 + 1)) sta = 1;
						else sta = 2;
					} else {
						if (len0 == len1) sta = 2;
						else if ((x && len1 == len0 + 2) || (!x && len0 == len1 + 2)) sta = 1;
						else continue;
					}
				} else {
					if (len & 1) {
						if ((x && len1 != len0 + 1) || (!x && len0 != len1 + 1)) continue;
					} else if (len0 != len1) continue;
				}
				int p0 = i - 1, p1 = m - 1, q0 = p0, q1 = p1;
				i64 sum = 0;
				v2[0] = sta == 1 ? 1E18 : 0;
				for (int k = 1, s = x; k <= len; k++, s ^= 1) {
					int nw = s ? ++p1 : ++p0;
					sum += v[nw];
					if (s) {
						for (; q0 < m - 1 && p[q0 + 1].id < p[nw].id; q0++) ;
						sum += max(q0 - p0, 0);
					} else {
						for (; q1 < j - 1 && p[q1 + 1].id < p[nw].id; q1++) ;
						sum += max(q1 - p1, 0);
					}
					if ((sta == 1 && ~k & 1) || (sta == 2 && k & 1)) v2[k] = 1E18;
					else v2[k] = sum;
				}
				upd(f[c][(x + len) & 1][y], o + v2[len]);
				p0 = m, p1 = j, q0 = p0, q1 = p1;
				sum = 0;
				for (int k = len, s = y; k; k--, s ^= 1) {
					int nw = s ? --p1 : --p0;
					sum += n + 1 - j - v[nw];
					if (s) {
						for (; q0 > i && p[q0 - 1].id > p[nw].id; q0--) ;
						sum += max(q0 - p0, 0);
					} else {
						for (; q1 > m && p[q1 - 1].id > p[nw].id; q1--) ;
						sum += max(q1 - p1, 0);
					}
					upd(f[c][(x + k - 1) & 1][(y + len + 1 - k) & 1], o + v2[k - 1] + sum);
				}
			}
	}
	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);
}