#include <bits/stdc++.h>
using namespace std;

const int MAX_N = 100024;

int a[MAX_N];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    freopen("negsort.in", "r", stdin);
    freopen("negsort.out", "w", stdout);

    int n, mina = INT_MAX;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        mina = min(mina, abs(a[i]));
    }

    int i = 0, ans = 0;
    while (fabs(a[i]) > mina) {
        if (a[i] > 0) {
            a[i] = -a[i];
            ans++;
        }
        i++;
    }

    int cntPos = 0, cntNeg = 0, save = i;
    while(fabs(a[i]) == mina) {
        if (a[i] > 0) cntPos++;
        if (a[i] < 0) cntNeg++;

        i++;
    }

    int currPos = 0, currNeg = 0, bestIdx = save, bestResult = min(cntPos, cntNeg);
    for (int j = save; j < i; j++) {
        if (a[j] > 0) currPos++;
        else if (a[j] < 0) currNeg++;

        if (bestResult > (j - save + 1 - currNeg + i - j - 1 - (cntPos - currPos))) {
            bestResult = (j - save + 1 - currNeg + i - j - 1 - (cntPos - currPos));
            bestIdx = j + 1;
        }
    }

    for (int j = save; j < bestIdx; j++) {
        if (a[j] > 0) {
            a[j] = -a[j];
            ans++;
        }
    }

    if (bestIdx != save) {
        for (int j = bestIdx; j < i; j++) {
            if (a[j] < 0) {
                a[j] = -a[j];
                ans++;
            }
        }
    }
    else {
        for (int j = save; j < i; j++) {
            if (cntPos >= cntNeg && a[j] < 0) {
                ans++;
                a[j] = -a[j];
            }
            else if (cntPos < cntNeg && a[j] > 0) {
                ans++;
                a[j] = -a[j];
            }
        }
    }

    while(i < n) {
        if (a[i] < 0) {
            a[i] = -a[i];
            ans++;
        }
        i++;
    }

    bool f = true;
    for (int i = 0; i < n - 1; i++) {
        if (a[i] > a[i + 1]) {
            f = false;
            break;
        }
    }

    cout << (f ? ans : -1) << endl;
    return 0;
}