#include<iostream>
#include<fstream>
#include<vector>
#include<queue>
#include<stack>
#include<math.h>
#include<algorithm>
#include<map>
#include<set>
#include<unordered_map>
#include<unordered_set>
using namespace std;

#define official

#ifdef official
#define cin inF
#define cout outF
#endif

ifstream inF("negsort.in");
ofstream outF("negsort.out");

const int MAX_N=100100;
long long a[MAX_N];
long long lp[MAX_N];
long long rn[MAX_N];
int ans;
int n;

void input()
{
    cin>>n;
    for (int i=0;i<n;++i)
    {
        cin>>a[i];
    }
}
void output()
{
    cout<<ans<<'\n';
}

int getOpt(int s, int f)
{
    int n=0;
    int p=0;
    for (int i=s;i<=f;++i)
    {
        lp[i]=p;
        if (a[i]>0) ++p;
    }
    for (int i=f;i>=s;--i)
    {
        if (i<f && a[i]<0) ++n;
        rn[i]=n;
    }
    int opt=-1;
    int curr;
    for (int i=s;i<=f;++i)
    {
        curr=lp[i]+rn[i];
        if (opt==-1 || curr<opt) opt=curr;
    }
    return opt;
}

void solve()
{
    if (n==1)
    {
        ans=0;
        return;
    }
    bool initinc;
    int turn=-1;
    int st=-1;
    for (int i=1;i<n;++i)
    {
        if (std::abs(a[i])==std::abs(a[i-1])) continue;
        st=i+1;
        if (std::abs(a[i])>std::abs(a[i-1])) initinc=1;
        else initinc=0;
        break;
    }

    if (st==-1)
    {
        ans=getOpt(0,n);
        return;
    }

    //cerr<<st<<" "<<initinc<<endl;

    for (int i=st;i<n;++i)
    {
        if (std::abs(a[i])>std::abs(a[i-1]))
        {
            //cerr<<"inc at "<<i<<" "<<initinc<<" "<<turn<<endl;
            if (initinc==0 && turn==-1) turn=i;
        }
        else if (std::abs(a[i])<std::abs(a[i-1]))
        {
            //cerr<<"dec at "<<i<<" "<<initinc<<" "<<turn<<endl;
            if (initinc==1) {turn=-2; break;}
            else if (initinc==0 && turn!=-1) {turn=-2; break;}
        }
    }
    if (turn==-2)
    {
        ans=-1;
        return;
    }
    ans=0;
    if (initinc==0 && turn==-1) turn=n;
    for (int i=0;i<n;++i)
    {
        if (initinc==1)
        {
            if (a[i]<0) ++ans;
        }
        else if (initinc==0)
        {
            if (i<turn)
            {
                if (a[i]>0) ++ans;
            }
            else
            {
                if (a[i]<0) ++ans;
            }
        }
    }
    if (initinc==0)
    {
        int stt;
        for (int i=turn-1;;--i)
        {
            if (std::abs(a[i])==std::abs(a[turn-1])) stt=i;
            else break;
        }
        int cnt=0;
        for (int i=stt;i<turn;++i)
        {
            if (a[i]>0) ++cnt;
        }
        ans-=cnt;
        ans+=getOpt(stt,turn);
    }
}

int main()
{
    input();
    solve();
    output();

    return 0;
}