#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
#endif
using ll = long long;
using ld = long double;
using ull = unsigned long long;
#define endl "\n"
typedef pair<int, int> Pii;
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REP3(i, m, n) for (int i = (m); (i) < int(n); ++ (i))
#define rep(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define ALL(x) begin(x), end(x)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(s) (s).begin(),(s).end()
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define rever(vec) reverse(vec.begin(), vec.end())
#define sor(vec) sort(vec.begin(), vec.end())
#define fi first
#define FOR_(n) for (ll _ = 0; (_) < (ll)(n); ++(_))
#define FOR(i, n) for (ll i = 0; (i) < (ll)(n); ++(i))
#define se second
#define pb push_back
#define P pair<ll,ll>
#define PQminll priority_queue<ll, vector<ll>, greater<ll>>
#define PQmaxll priority_queue<ll,vector<ll>,less<ll>>
#define PQminP priority_queue<P, vector<P>, greater<P>>
#define PQmaxP priority_queue<P,vector<P>,less<P>>
#define NP next_permutation
//const ll mod = 1000000009;
//const ll mod = 998244353;
const ll mod = 1000000007;
const ll inf = 4100000000000000000ll;
const ld eps = ld(0.00000000001);
static const long double pi = 3.141592653589793;
template<class T>void vcin(vector<T> &n){for(int i=0;i<int(n.size());i++) cin>>n[i];}
template<class T,class K>void vcin(vector<T> &n,vector<K> &m){for(int i=0;i<int(n.size());i++) cin>>n[i]>>m[i];}
template<class T>void vcout(vector<T> &n){for(int i=0;i<int(n.size());i++){cout<<n[i]<<" ";}cout<<endl;}
template<class T>void vcin(vector<vector<T>> &n){for(int i=0;i<int(n.size());i++){for(int j=0;j<int(n[i].size());j++){cin>>n[i][j];}}}
template<class T>void vcout(vector<vector<T>> &n){for(int i=0;i<int(n.size());i++){for(int j=0;j<int(n[i].size());j++){cout<<n[i][j]<<" ";}cout<<endl;}cout<<endl;}
void yes(bool a){cout<<(a?"yes":"no")<<endl;}
void YES(bool a){cout<<(a?"YES":"NO")<<endl;}
void Yes(bool a){cout<<(a?"Yes":"No")<<endl;}
void possible(bool a){ cout<<(a?"possible":"impossible")<<endl; }
void Possible(bool a){ cout<<(a?"Possible":"Impossible")<<endl; }
void POSSIBLE(bool a){ cout<<(a?"POSSIBLE":"IMPOSSIBLE")<<endl; }
#define FOR_R(i, n) for (ll i = (ll)(n)-1; (i) >= 0; --(i))
template<class T>auto min(const T& a){ return *min_element(all(a)); }
template<class T>auto max(const T& a){ return *max_element(all(a)); }
template<class T,class F>void print(pair<T,F> a){cout<<a.fi<<" "<<a.se<<endl;}
template<class T>bool chmax(T &a,const T b) { if (a<b) { a=b; return 1; } return 0;}
template<class T>bool chmin(T &a,const T b) { if (b<a) { a=b; return 1; } return 0;}
template<class T> void ifmin(T t,T u){if(t>u){cout<<-1<<endl;}else{cout<<t<<endl;}}
template<class T> void ifmax(T t,T u){if(t>u){cout<<-1<<endl;}else{cout<<t<<endl;}}
ll fastgcd(ll u,ll v){ll shl=0;while(u&&v&&u!=v){bool eu=!(u&1);bool ev=!(v&1);if(eu&&ev){++shl;u>>=1;v>>=1;}else if(eu&&!ev){u>>=1;}else if(!eu&&ev){v>>=1;}else if(u>=v){u=(u-v)>>1;}else{ll tmp=u;u=(v-u)>>1;v=tmp;}}return !u?v<<shl:u<<shl;}
ll modPow(ll a, ll n, ll mod) { if(mod==1) return 0;ll ret = 1; ll p = a % mod; while (n) { if (n & 1) ret = ret * p % mod; p = p * p % mod; n >>= 1; } return ret; }
vector<ll> divisor(ll x){ vector<ll> ans; for(ll i = 1; i * i <= x; i++){ if(x % i == 0) {ans.push_back(i); if(i*i!=x){ ans.push_back(x / ans[i]);}}}sor(ans); return ans; }
ll pop(ll x){return __builtin_popcountll(x);}
ll poplong(ll x){ll y=-1;while(x){x/=2;y++;}return y;}
P hyou(P a){ll x=fastgcd(abs(a.fi),abs(a.se));a.fi/=x;a.se/=x;if(a.se<0){a.fi*=-1;a.se*=-1;}return a;}
P Pplus(P a,P b){ return hyou({a.fi*b.se+b.fi*a.se,a.se*b.se});}
P Ptimes(P a,ll b){ return hyou({a.fi*b,a.se});}
P Ptimes(P a,P b){ return hyou({a.fi*b.fi,a.se*b.se});}
P Pminus(P a,P b){ return hyou({a.fi*b.se-b.fi*a.se,a.se*b.se});}
P Pgyaku(P a){ return hyou({a.se,a.fi});}
template<class T>
struct Sum{
  vector<T> data;
  Sum(const vector<T>& v):data(v.size()+1){
    for(ll i=0;i<v.size();i++) data[i+1]=data[i]+v[i];
  }
  T get(ll l,ll r) const {
    return data[r]-data[l];
  }
};
template<class T>
struct Sum2{
  vector<vector<T>> data;
  Sum2(const vector<vector<T>> &v):data(v.size()+1,vector<T>(v[0].size()+1)){
    for(int i=0;i<v.size();i++) for(int j=0;j<v[i].size();j++) data[i+1][j+1]=data[i][j+1]+v[i][j];
    for(int i=0;i<v.size();i++) for(int j=0;j<v[i].size();j++) data[i+1][j+1]+=data[i+1][j];
  }
  T get(ll x1,ll y1,ll x2,ll y2) const {
    return data[x2][y2]+data[x1][y1]-data[x1][y2]-data[x2][y1];
  }
};
 
void cincout(){
  ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
  cout<< fixed << setprecision(15);
}
struct nd{
  ll l,r,x,sum;
  nd(ll L,ll R,ll X,ll SUM){
    l=L,r=R,x=X;
    sum=SUM;
  }
};
nd op(nd a,nd b){
  return nd(a.l+b.l,a.r+b.r,a.x+b.x,a.sum+b.sum+a.r*(b.x+b.l)+b.l*a.x);
}
struct Segtree{
  vector<ll> node;
  ll n;
  Segtree(ll N){
    n=1;
    while(n<N) n*=2;
    node.resize(2*n);
    for(int i=0;i<N;i++) node[i+n]=1;
    for(int i=N-1;i>=1;i--) node[i]=node[i*2]+node[i*2+1];
  }
  void set(int x,ll y){
    x+=n;
    node[x]+=y;
    x/=2;
    while(x){
      node[x]=node[2*x]+node[2*x+1];
      x/=2;
    }
  }
  ll prod(ll l,ll r,ll a,ll b,ll k){
    if(r<=a||b<=l) return 0;
    if(l<=a&&b<=r) return node[k];
    return (prod(l,r,a,(a+b)/2,2*k)+prod(l,r,(a+b)/2,b,2*k+1));
  }
  ll prod(ll l,ll r){
    return prod(l,r,0,n,1);
  }
};
ll dp[501010][2][2];
int main(){
  cincout();
  int n;
  cin>>n;
  vector<int> a(n);
  vcin(a);
  map<int,int> M;
  M[0]++;
  for(auto e:a) M[abs(e)]++;
  int M2=0;
  for(auto &e:M){
    e.se=M2;
    M2++;
  }
  for(int i=0;i<n;i++){
    if(a[i]<0) a[i]=M[-a[i]]*-1;
    else a[i]=M[a[i]];
  }
  Segtree seg(n);
  dp[n+3][0][0]=dp[n+3][0][1]=dp[n+3][1][0]=dp[n+3][1][1]=0;
  vector<vector<int>> idx(n+3);
  for(int i=0;i<n;i++) idx[abs(a[i])].pb(i);
  for(auto e:idx) assert(1>=e.size());
  for(int i=n+2;i>=1;i--){
    //dp[i+1] -> dp[i]
    vector<int> od,ev;
    for(auto e:idx[i]){
      if((a[e]>0)^(e%2==0)){
        od.pb(e);
      }
      else{
        ev.pb(e);
      }
    }
    for(int j=0;j<2;j++){
      for(int k=0;k<2;k++) dp[i][j][k]=inf;
    }
    for(auto e:od) seg.set(e,-1);
    for(auto e:ev) seg.set(e,-1);
  /*  cerr<<i<<endl;
    for(auto e:od) cerr<<e<<" ";
    cerr<<endl;
    for(auto e:ev) cerr<<e<<" ";
    cerr<<endl; */
    if(od.size()){
      for(int k=0;k<2;k++){
        chmin(dp[i][1][k],dp[i+1][0][k]+seg.prod(0,od[0]));
        chmin(dp[i][k][1],dp[i+1][k][0]+seg.prod(od[0],n));
      }
    }
    else if(ev.size()){
      for(int k=0;k<2;k++){
        chmin(dp[i][0][k],dp[i+1][1][k]+seg.prod(0,ev[0]));
        chmin(dp[i][k][0],dp[i+1][k][1]+seg.prod(ev[0],n));
      }
    }
    else{
      for(int j=0;j<2;j++){
        for(int k=0;k<2;k++){
          dp[i][j][k]=dp[i+1][j][k];
        }
      }
    }
  }
  ll ans=inf;
  for(int j=0;j<2;j++){
    for(int k=0;k<2;k++){
      chmin(ans,dp[1][j][k]);
    }
  }
  if(ans==inf) ans=-1;
  cout<<ans<<endl;
}