#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
const int MAXN = 5e5 + 5;
const ll linf = 0x3f3f3f3f3f3f3f3f;

void chk_min(ll &a,ll b){ if(a>b) a=b;}

struct BIT
{
	int tree[MAXN], n;
	#define lowbit(x) ((x)&-(x))
	void update(int x,int k)
	{
		while(x<=n)
			tree[x] += k, x += lowbit(x);
	}
	int query(int x)
	{
		int res = 0;
		while(x)
			res += tree[x], x ^= lowbit(x);
		return res;
	}
	int query(int l,int r)
	{
		return query(r) - query(l-1);
	}
	int kth(int k)
	{
		int res = 0;
		for(int i=1<<20; i; i>>=1)
			if(res+i<=n && tree[res+i]<k)
				res += i, k -= tree[res];
		return res + 1;
	}
}tree;

int n;
int h[MAXN];

void getres(vector<int> pos, int type, array<ll,2> &f)
{
	vector<int> p[2];
	for(int i=0; i<(int)pos.size(); ++i)
	{
		int x = h[pos[i]] > 0;
		if((tree.query(pos[i]) + i) & 1) x ^= 1;
		if(type) x ^= 1;
		p[x].emplace_back(pos[i]);
	}
	
	int tot0 = tree.query(n);
	
	if(tot0 & 1)
	{
		int delta = (int)p[0].size() - (int)p[1].size();
		if(delta < 0 || delta > 1) return;
		
		vector<int> a;
		for(int i=0; i<(int)p[1].size(); ++i)
			a.emplace_back(p[0][i]), a.emplace_back(p[1][i]);
		if(delta)
			a.emplace_back(p[0].back());
		
		ll cur = 0;
		for(int i: a)
		{
			cur += tree.query(i, n);
			tree.update(i, 1);
		}
		for(int i: a)
			tree.update(i, -1);
		
		for(int i=0; i<=(int)a.size(); ++i)
		{
			chk_min(f[i&1], cur);
			
			if(i == (int)a.size()) break;
			
			cur -= tree.query(a[i], n);
			cur += tree.query(1, a[i]);
		}
		return;
	}
	
	int need = (int)pos.size() / 2;
	
	if(need == (int)p[0].size())
	{
		vector<int> a;
		for(int i=0; i<(int)p[0].size(); ++i)
			a.emplace_back(p[1][i]), a.emplace_back(p[0][i]);
		if((int)p[1].size() > (int)p[0].size())
			a.emplace_back(p[1].back());
		
		ll cur = 0;
		for(int i: a)
		{
			cur += tree.query(i, n);
			tree.update(i, 1);
		}
		for(int i: a)
			tree.update(i, -1);
		
		for(int i=0; i<=(int)a.size(); i+=2)
		{
			chk_min(f[i&1], cur);
			
			if(i+1 >= (int)a.size()) continue;
			
			cur += - tree.query(a[i], n) + tree.query(1, a[i]);
			cur += - tree.query(a[i+1], n) + tree.query(1, a[i+1]);
			
			cur += a[i] < a[i+1]? 1: -1;
		}
	}
	else if(need + 1 == (int)p[0].size())
	{
		vector<int> a = {p[0][0]};
		p[0].erase(p[0].begin());
		
		for(int i=0; i<(int)p[1].size(); ++i)
			a.emplace_back(p[0][i]), a.emplace_back(p[1][i]);
		if((int)p[0].size() > (int)p[1].size())
			a.emplace_back(p[0].back());
		
		ll cur = 0;
		for(int i: a)
		{
			cur += tree.query(i, n);
			tree.update(i, 1);
		}
		for(int i: a)
			tree.update(i, -1);
		
		cur += - tree.query(a[0], n) + tree.query(1, a[0]);
		
		for(int i=1; i<=(int)a.size(); i+=2)
		{
			chk_min(f[i&1], cur);
			
			if(i+1 >= (int)a.size()) continue;
			
			cur += - tree.query(a[i], n) + tree.query(1, a[i]);
			cur += - tree.query(a[i+1], n) + tree.query(1, a[i+1]);
			
			cur += a[i] < a[i+1]? 1: -1;
		}
	}
	
	return;
}

int main(void)
{
	scanf("%d",&n);
	for(int i=1; i<=n; ++i)
		scanf("%d",&h[i]);
	
	tree.n = n;
	for(int i=1; i<=n; ++i)
		tree.update(i, 1);
	
	vector<pii> vec;
	for(int i=1; i<=n; ++i)
		if(h[i]) vec.emplace_back(-abs(h[i]), i);
	sort(vec.begin(), vec.end());
	
	array<ll,2> f = {0, linf};
	for(int i=0,j=0; i<(int)vec.size(); i=j)
	{
		while(j<(int)vec.size() && vec[i].first == vec[j].first)
			++j;
		
		vector<int> pos;
		for(int k=i; k<j; ++k)
			pos.emplace_back(vec[k].second);
		
		for(auto k: pos)
			tree.update(k, -1);
		
		array<ll,2> nf = {linf, linf};
		for(int t=0; t<=1; ++t)
		{
			if(f[t] == linf) continue;
			array<ll,2> cur = {linf, linf};
			getres(pos, t, cur);
			nf[0 ^ t] = min(nf[0 ^ t], cur[0] + f[t]);
			nf[1 ^ t] = min(nf[1 ^ t], cur[1] + f[t]);
		}
		f = nf;
	}
	
	ll ans = min(f[0], f[1]);
	printf("%lld\n",ans == linf? -1: ans);
	return 0;
}