#include <iostream>
#include <algorithm>
#include<cmath>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<iomanip>
#include<ctime>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<bitset>
#include<cassert>
#define sqr(x) ((x)*(x))
#define fz1(i,n) for ((i)=1;(i)<=(n);(i)++)
#define fd1(i,n) for ((i)=(n);(i)>=1;(i)--)
#define fz0g(i,n) for ((i)=0;(i)<=(n);(i)++)
#define fd0g(i,n) for ((i)=(n);(i)>=0;(i)--)
#define fz0k(i,n) for ((i)=0;(i)<(n);(i)++)
#define fd0k(i,n) for ((i)=(((long long)(n))-1);(i)>=0;(i)--)
#define fz(i,x,y) for ((i)=(x);(i)<=(y);(i)++)
#define fd(i,y,x) for ((i)=(y);(i)>=(x);(i)--)
#define fzin fz1(i,n)
#define fzim fz1(i,m)
#define fzjn fz1(j,n)
#define fzjm fz1(j,m)
#define ff(c,itr) for (__typeof((c).begin()) itr=(c).begin();itr!=(c).end();++itr)
#define pb push_back
#define mk make_pair
#define rdst(st,len){static char ss[len];scanf(" %s",ss);(st)=ss;}
#define spln(i,n) (i==n?'\n':' ')
#define fac_init(n){fac[0]=fac[1]=inv[1]=fi[0]=fi[1]=1;fz(i,2,n){fac[i]=1ll*fac[i-1]*i%mod;inv[i]=1ll*(mod-mod/i)*inv[mod%i]%mod;fi[i]=1ll*fi[i-1]*inv[i]%mod;}}
using namespace std;
typedef long long i64;
typedef long double f80;
typedef unsigned int u32;
typedef unsigned long long u64;
//typedef __int128 i128;
//typedef unsigned __int128 u128;
#ifndef ONLINE_JUDGE
	FILE *___=freopen("1.in","r",stdin);
#endif
inline void read(int &x)
{
	char c;int f=1;
	while(!isdigit(c=getchar()))if(c=='-')f=-1;
	x=(c&15);while(isdigit(c=getchar()))x=(x<<1)+(x<<3)+(c&15);
	x*=f;
}
int n,m,c,i,j,k,a[500005];
vector<int> vo[500005],ve[500005];
vector<int> all;
i64 f[2005][2005];
int main()
{
	read(n);all.push_back(0);fz1(i,n)read(a[i]),all.push_back(abs(a[i]));sort(all.begin(),all.end());all.resize(unique(all.begin(),all.end())-all.begin());
	fz1(i,n){
		int t=lower_bound(all.begin(),all.end(),abs(a[i]))-all.begin();
		if((a[i]==0)||((i&1)==(a[i]<0))) vo[t].push_back(i); else ve[t].push_back(i);
	}
	memset(f,0x3f,sizeof(f));f[all.size()][0]=0;
	fd1(i,all.size()-1){
		fz0g(j,c)if(f[i+1][j]<0x3f3f3f3f3f3f3f3fll){
			int l=j+1,r=n-(c-j),l0=l+(l&1),l1=l+(!(l&1)),r0=r-(!(r&1)),r1=r-(r&1);
			i64 cur=f[i+1][j];
			fd0k(k,vo[i].size()) cur+=abs(vo[i][k]-r1),r1-=2;
			fd0k(k,ve[i].size()) cur+=abs(ve[i][k]-r0),r0-=2;
			int nj=j;if(abs(l0-l1)==1&&abs(r0-r1)==1) f[i][nj]=min(f[i][nj],cur);
			int k0=0,k1=0;for(;;){
				nj++;
				if(l0<l1){
					if(k0==ve[i].size()) break;
					r0+=2;cur-=abs(ve[i][k0]-r0);
					cur+=abs(ve[i][k0]-l0);l0+=2;
					k0++;
				}
				else{
					if(k1==vo[i].size()) break;
					r1+=2;cur-=abs(vo[i][k1]-r1);
					cur+=abs(vo[i][k1]-l1);l1+=2;
					k1++;
				}
				if(abs(l0-l1)==1&&abs(r0-r1)==1) f[i][nj]=min(f[i][nj],cur);
			}
		}
		c+=vo[i].size()+ve[i].size();
	}
	i64 ans=0x3f3f3f3f3f3f3f3fll;
	fz0g(j,c)if(f[1][j]<0x3f3f3f3f3f3f3f3fll){
		i64 cur=f[1][j];
		fz0k(k,vo[0].size()) cur+=abs(vo[0][k]-(i+k+1));
		ans=min(ans,cur);
	}
	if(ans==0x3f3f3f3f3f3f3f3fll) puts("-1"); else printf("%lld\n",ans/2);
	return 0;
}