#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#define ll long long
#define inf 1000000000000ll
using namespace std;
int n;
int _abs(int x){
	if (x<0)return -x;
	return x;
}
struct node{
	int p,v;
	bool operator <(const node &y)const{
		if (_abs(v)!=_abs(y.v))return _abs(v)<_abs(y.v);
		if (v!=y.v)return v<y.v;
		return p<y.p;
	}
}a[1000005];
struct BIT{
	int tree[1000005];
	void clear(){
		memset(tree,0,sizeof(tree));
		return;
	}
	void add(int p,int v){
		while(p<=n)tree[p]+=v,p+=(p&(-p));
		return;
	}
	int ask(int p){
		int ans=0;
		while(p)ans+=tree[p],p-=(p&(-p));
		return ans;
	}
}bit;
ll c[1000005][2];
ll f[1000005][2];
int t0[1000005],t1[1000005];
int pos[1000005];
ll ask(int len){
	ll ans=0;
	for (int i=1;i<=len;i++)
		if (pos[i]==0)return inf;
	for (int i=1;i<=len;i++){
		ans+=bit.ask(n)-bit.ask(pos[i]);
		bit.add(pos[i],1);
	}
	for (int i=1;i<=len;i++)bit.add(pos[i],-1);
	return ans;
}
int get_o(int o,int x){
	return ((x-1)&1)^o;
}
ll dfs(int now,int o){
	if (f[now][o]!=-1)return f[now][o];
	if (now==0)return 0;
	if (a[now].v==0)return 0;
	int l=now,r=now;
	while(l>1&&_abs(a[l-1].v)==_abs(a[r].v))l--;
	int l0=0,l1=0;
	for (int i=l;i<=r;i++)
		if (a[i].v<0)t0[++l0]=a[i].p;
		else t1[++l1]=a[i].p;
	int len=r-l+1;
	ll ans=inf;
	for (int i=0;i<=len;i++){
		int cnt0=0,cnt1=0;
		ll s=0;
		for (int j=1;j<=i;j++){
			if (get_o(o,j)==1)pos[j]=t0[++cnt0];
			else pos[j]=t1[++cnt1];
			s+=c[pos[j]][0];
		}
		for (int j=i+1;j<=len;j++){
			if (get_o(o,now-(len-j))==0)pos[j]=t0[++cnt0];
			else pos[j]=t1[++cnt1];
			s+=c[pos[j]][1];
		}
		if (cnt0==l0&&cnt1==l1)ans=min(ans,s+ask(len)+dfs(l-1,get_o(o,i+1)));
	}
	return f[now][o]=ans;
}
int main(){
	scanf("%d",&n);
	for (int i=1;i<=n;i++){
		a[i].p=i;
		scanf("%d",&a[i].v);
		if (i&1)a[i].v=-a[i].v;
	}
	sort(a+1,a+1+n);
	int j=1;
	for (int i=1;i<=n;i++){
		while(_abs(a[j].v)<_abs(a[i].v))bit.add(a[j].p,1),j++;
		c[a[i].p][0]=bit.ask(a[i].p-1);
		c[a[i].p][1]=bit.ask(n)-bit.ask(a[i].p);
	}
	c[0][0]=c[0][1]=inf;
	bit.clear();
	memset(f,-1,sizeof(f));
	ll ans=dfs(n,0);
	if (ans==inf)ans=-1;
	cout<<ans<<endl;
	return 0;
}