#include <bits/stdc++.h>
#define filein(str) freopen(str, "r", stdin)
#define fileout(str) freopen(str, "w", stdout);
using namespace std;

int nums[1000005];

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

	filein("negsort.in");
    fileout("negsort.out");

    int n;
    cin >> n;
    for(int i = 0; i < n; i++) cin >> nums[i];

    int i = 0;
    long long ans1 = 0;
    bool res = false;

    while(i < n - 1 and abs(nums[i]) <= abs(nums[i + 1])) {
        if(nums[i] < 0) ans1++;
        i++;
    }
    if(i == n - 1) {
        if(nums[i] < 0) ans1++;
        res = true;
    }

    i = 0;
    long long ans = 0;
    while(i < n - 1 and abs(nums[i]) >= abs(nums[i + 1])) {
        if(nums[i] > 0) ans++;
        i++;
    }

    int j = i, curRes = 0, bestRes = 0;
    while(i > 0 and abs(nums[i]) == abs(nums[i - 1])) {
        if(nums[i] > 0) curRes++;
        else curRes--;
        if(curRes > bestRes) {
            bestRes = curRes;
            j = i;
        }
        i--;
    }
    ans -= bestRes;
    bool flag = false;
    if(j != n - 1) i = j - 1;
    else i = j, flag = true;
    if(i != n - 1) i++;
    else flag = true;
    while(i < n - 1 and abs(nums[i]) <= abs(nums[i + 1])) {
        if(nums[i] < 0) ans++;
        i++;
    }

    if(i != n - 1) cout << -1 << endl;
    else {
        if(nums[i] < 0 and !flag) ans++;
        if(res) cout << min(ans1, ans) << endl;
        else cout << ans << endl;
    }
}
/*
5
1 1 1 -1 -1

11
2 2 -1 -1 1 1 1 1 -1 1 1
*/