//code by Emissary
#include<bits/stdc++.h>

#define fi first
#define se second
#define vc vector
#define db double
#define ll long long
#define mk make_pair
#define pb push_back
#define PI pair<int,int>
#define ull unsigned long long
#define err cerr << "   -_-   " << endl
#define debug cerr << " ------------------- " << endl

#define input(x) freopen(#x".in","r",stdin)
#define output(x) freopen(#x".out","w",stdout)

#define NO puts("No")
#define YES puts("Yes")

//#define int long long

using namespace std;

namespace IO{
	inline int read(){
		int X=0, W=0; char ch=getchar();
		while(!isdigit(ch)) W|=ch=='-', ch=getchar();
		while(isdigit(ch)) X=(X<<1)+(X<<3)+(ch^48), ch=getchar();
		return W?-X:X;
	}
	inline void write(ll x){
		if(x<0) x=-x, putchar('-');
		if(x>9) write(x/10);
		putchar(x%10+'0');
	}
	inline void sprint(ll x){write(x), putchar(32);}
	inline void eprint(ll x){write(x), putchar(10);}
}using namespace IO;

const int MAXN = 5e5+5;

int n, a[MAXN], tree[3][MAXN], mu[2]={-1,1}, ans[MAXN];
int tot[2], k0, k1, le[MAXN], ri[MAXN], topf, stk[MAXN], uL[MAXN][2], uR[MAXN][2];

vc<int> col[2];

ll v1[MAXN], v2[MAXN];
ll dp[2][2], g[2][2];

struct NUM{
	int v, col, id;
	inline bool friend operator < (const NUM &x, const NUM &y){
		return x.v>y.v;
	}
}num[MAXN];

inline int lowbit(int x){return x & -x;}

inline void add(int x, int v, int t){
	while(x<=n) tree[t][x]+=v, x+=lowbit(x);
	return ;
}

inline int ask(int x, int t){
	int s=0;
	while(x) s+=tree[t][x], x^=lowbit(x);
	return s;
}

inline int query(int l, int r, int t){return ask(r,t)-ask(l-1,t);}

inline void op(int l, int r){
	//cerr << "op:" << l << ' ' << r << endl;
	memset(g,127/3,sizeof g);
	col[0].clear(); col[1].clear();
	for(int i=l;i<=r;++i) col[num[i].col].pb(num[i].id), add(num[i].id,-1,0);
	for(int i=l;i<=r;++i){
		le[num[i].id]=query(1,num[i].id-1,0);
		ri[num[i].id]=query(num[i].id+1,n,0);
		cerr << "ID:" << num[i].id << ' ' << num[i].col << endl;
	}
	sort(col[0].begin(),col[0].end());
	sort(col[1].begin(),col[1].end());
	int L[2], R[2];
	for(int i=0;i<2;++i){
		for(int j=0;j<2;++j){
			if(dp[i][j]>1ll*n*n) continue;
			//cerr << "dp:" << i << ' ' << j << ' ' << dp[i][j] << endl;
			ll s=0; int now=i; L[0]=L[1]=0;
			int len=col[0].size()+col[1].size();
			for(int k=1;k<=len;++k) v1[k]=v2[k]=1e18;
			for(int k=1;k<=len;++k){
				if(L[now]==col[now].size()) break;
				int c=col[now][L[now]]; L[now]++;
				v1[k]=v1[k-1]+query(c+1,n,1); add(c,1,1); stk[++topf]=c;
				now^=1; uL[k][0]=L[0], uL[k][1]=L[1];
				//cerr << "v1:" << k << ' ' << v1[k] << endl;
			}
			//err;
			while(topf) add(stk[topf],-1,1), --topf; now=j;
			R[0]=(int)col[0].size()-1; R[1]=(int)col[1].size()-1;
			uR[0][0]=R[0], uR[0][1]=R[1];
			//err;
			for(int k=1;k<=len;++k){
				if(R[now]<0) break;
				int c=col[now][R[now]]; R[now]--;
				v2[k]=v2[k-1]+query(1,c-1,1); add(c,1,1); stk[++topf]=c;
				now^=1; uR[k][0]=R[0], uR[k][1]=R[1];
			//	cerr << "v2:" << k << ' ' << v2[k] << endl;
			}
			//err;
			while(topf) add(stk[topf],-1,1), --topf;
			for(auto k:col[0]) s+=ri[k], add(k,1,1);
			for(auto k:col[1]) s+=ri[k], add(k,1,1);
			int A, B; now=i; L[0]=L[1]=0; ll S=0;
			for(int k=0;k<=len;++k){
				A=k&1, B=(len-k)&1;
				if(uL[k][0]-1==uR[len-k][0] && uL[k][1]-1==uR[len-k][1]) g[i^A][j^B]=min(g[i^A][j^B],dp[i][j]+s+S+v1[k]+v2[len-k]);
				if(k!=len){
					if(L[now]==col[now].size()) break;
					int c=col[now][L[now]]; L[now]++;
					now^=1; S-=query(c+1,n,2); add(c,-1,1); S+=query(1,c-1,1); add(c,1,2); stk[++topf]=c; s+=le[c]-ri[c];
				}
			}
			while(topf) add(stk[topf],-1,2), --topf;
		}
	}
	for(int i=0;i<2;++i)
		for(int j=0;j<2;++j) dp[i][j]=g[i][j];
	return ;
}

signed main(){
	n=read(); int c=0;
	for(int i=1;i<=n;++i) a[i]=read()*mu[i%2], c+=a[i]==0;
	for(int i=1;i<=n;++i){
		//cerr << "a[i]=" << a[i] << endl;
		if(a[i]<0) num[i].col=1;
		else num[i].col=0; num[i].v=abs(a[i]); num[i].id=i;
	}
	sort(num+1,num+1+n);
	int L, R, las;
	if(n%2==0) L=R=1;
	else L=1, R=0; las=1;
	memset(dp,127/3,sizeof dp); dp[L][R]=0;
	for(int i=1;i<=n;++i) add(i,1,0);
	for(int i=2;i<=n-c;++i){
		if(num[i].v!=num[i-1].v){
			op(las,i-1);
			las=i;
		}
	}
	if(c!=n) op(las,n-c); ll ans=min(min(dp[0][0],dp[0][1]),min(dp[1][1],dp[1][0]));
	eprint(ans>1ll*n*n?-1:ans);
	return 0;
}