#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
template <typename T> inline void read(T &F) {
    int R = 1; F = 0; char CH = getchar();
    for(; !isdigit(CH); CH = getchar()) if(CH == '-') R = -1;
    for(; isdigit(CH); CH = getchar()) F = F * 10 + CH - 48;
    F *= R;
}
inline void file(string str) {
    freopen((str + ".in").c_str(), "r", stdin);
    freopen((str + ".out").c_str(), "w", stdout);
}
const int N = 5e5 + 10;
int n, ai[N]; map<int, vector<int> > M;
struct BIT {
    int c[N]; vector<int> rub;
    void add(int x) {
        rub.emplace_back(x);
        for(; x <= n; x += (x & -x)) c[x]++;
    }
    void del(int x) {
        for(; x <= n; x += (x & -x)) c[x]--;
    }
    int qry(int x) {
        int res = 0;
        for(; x; x -= (x & -x))
            res += c[x];
        return res;
    }
    int qry(int l, int r) {
        return qry(r) - qry(l - 1);
    }
    void clr() {
        for(int i : rub)
            for(int j = i; j <= n; j += (j & -j)) c[j] = 0;
    }
}tr, G;
LL calc(vector<int> c) {
    reverse(c.begin(), c.end());
    LL ans = 0; 
    for(int i : c) {
        //cerr << i << ' ';
        ans += tr.qry(i);
        tr.add(i);
    }
    //cerr << ans << "??" << endl;
    tr.clr(); return ans;
}
void chkmin(LL &x, LL y) {
    //cerr << x << ' ' << y << "!!" << endl;
    x = (x < y ? x : y);
} 
LL f[2][2], g[2][2];
void calc(int x, int l, int r, LL y) {
    //cerr << x << ' ' << l << ' ' << r << endl;
    const int u = M[x].size(), v = M[-x].size(), m = u + v;
    if((m + (r & 1)) / 2 == v) {
        vector<int> c[2] = {M[x], M[-x]}; 
        int L = l, R = r - m + 1; vector<int> tmp;
        LL res = 0;
        for(int i = r - m + 1; i <= r; i++)
            tmp.emplace_back(c[abs(i) & 1].back()), res += G.qry(c[abs(i) & 1].back(), n), c[abs(i) & 1].pop_back();
        res += calc(tmp);
        chkmin(g[L & 1][abs(R - 1) & 1], res + y);
        c[0] = M[x], c[1] = M[-x]; 
        for(int i = 2; i <= m; i += 2) {
            res -= c[abs(R) & 1].back() > c[abs(R + 1) & 1].back(); R += 2;
            res += c[abs(L + 1) & 1].back() > c[abs(L) & 1].back(); L += 2;
            res -= G.qry(c[0].back(), n); res -= G.qry(c[1].back(), n);
            res += G.qry(c[0].back()); res += G.qry(c[1].back());
            c[0].pop_back(), c[1].pop_back();
            chkmin(g[L & 1][abs(R - 1) & 1], res + y);
        }
    }
    if(m >= 1 && (m - 1 + (r & 1)) / 2 + ((l ^ 1) & 1) == v) {
        //cerr << "??" << endl;
        vector<int> c[2] = {M[x], M[-x]};
        int L = l + 1, R = r - m + 2; vector<int> tmp; LL res = 0;
        tmp.emplace_back(c[(l ^ 1) & 1].back()); res += G.qry(c[(l ^ 1) & 1].back()); c[(l ^ 1) & 1].pop_back();
        for(int i = r - m + 2; i <= r; i++)
            tmp.emplace_back(c[i & 1].back()), res += G.qry(c[i & 1].back(), n), c[i & 1].pop_back();
        res += calc(tmp);
        c[0] = M[x], c[1] = M[-x]; c[(l ^ 1) & 1].pop_back();
        chkmin(g[L & 1][abs(R - 1) & 1], res + y);
        for(int i = 3; i <= m; i += 2) {
            res -= c[abs(R) & 1].back() > c[abs(R + 1) & 1].back(); R += 2;
            res += c[abs(L + 1) & 1].back() > c[abs(L) & 1].back(); L += 2;
            res -= G.qry(c[0].back(), n); res -= G.qry(c[1].back(), n);
            res += G.qry(c[0].back()); res += G.qry(c[1].back());
            c[0].pop_back(), c[1].pop_back();
            chkmin(g[L & 1][abs(R - 1) & 1], res + y);
        }
    }
}
int main() {
    //file("test");
    read(n); vector<int> R;
    for(int i = 1; i <= n; i++) {
        read(ai[i]);
        if(i & 1) ai[i] = -ai[i];
        M[ai[i]].emplace_back(i);
        R.emplace_back(abs(ai[i]));
        G.add(i);
    }
    sort(R.begin(), R.end());
    R.erase(unique(R.begin(), R.end()), R.end());
    reverse(R.begin(), R.end());
    for(auto &i : M) sort(i.second.begin(), i.second.end(), greater<int>());
    memset(f, 0x3f, sizeof(f)); f[1][n & 1] = 0;
    for(int i : R) {
        if(i == 0) continue;
        for(int j : M[i]) G.del(j); for(int j : M[-i]) G.del(j);
        memset(g, 0x3f, sizeof(g));
        for(int a = 0; a <= 1; a++)
            for(int b = 0; b <= 1; b++)
                if(f[a][b] <= 1LL * n * n) calc(i, a, b, f[a][b]);
        swap(f, g);
    }
    LL ans = 1e18;
    for(int i = 0; i <= 1; i++)
        for(int j = 0; j <= 1; j++) ans = min(ans, f[i][j]);
    if(ans > 1LL * n * n) puts("-1");
    else cout << ans << '\n';
    
    #ifdef _MagicDuck
        fprintf(stderr, "# Time: %.3lf s", (double)clock() / CLOCKS_PER_SEC);
    #endif
    return 0;
}