#include <bits/stdc++.h>
#pragma optimize ("O3")
//#pragma target ("sse4")
const int MAXN=200017;
const int INF=1e9+17;
using namespace std;
#define endl '\n'

int dp[MAXN][4], a[MAXN], n;
void mainp()
{
    freopen ("negsort.in","r",stdin);
    freopen ("negsort.out","w",stdout);
    cin>>n;
    for(int i=0; i<n; i++) cin>>a[i];
    for(int i=0; i<MAXN; i++) dp[i][0]=dp[i][1]=dp[i][2]=dp[i][3]=INF;
    dp[0][0]=dp[0][2]=0;
    dp[0][1]=dp[0][3]=1;
    for(int i=1; i<n; i++)
    {
        if(a[i]>=a[i-1]) {dp[i][0]=min(dp[i-1][0], dp[i-1][2]); }
        if(a[i]>=(-a[i-1])) {dp[i][2]=min(dp[i-1][1], dp[i-1][3]); }
        if((-a[i])>=a[i-1]) {dp[i][1]=min(dp[i-1][0], dp[i-1][2])+1; }
        if((-a[i])>=(-a[i-1])) {dp[i][3]=min(dp[i-1][1], dp[i-1][3])+1; }
        //cout<<i<<" "<<dp[i][0]<<" "<<dp[i][1]<<" "<<dp[i][2]<<" "<<dp[i][3]<<endl;
    }
    
    int ans=min(min(dp[n-1][0], dp[n-1][1]), min(dp[n-1][2], dp[n-1][3]));
    if(ans>=INF) cout<<-1<<endl;
    else cout<<ans<<endl;
}
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    mainp();
    return 0;
}