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#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back

const int MAKS = 1e6 + 2;

const ll INF = 1e9;


ll kopia1[MAKS];
ll kopia2[MAKS];

ll check(int n, ll pom[], ll parity)
{

    ll prev = pom[0];
    ll change = 0;

    for(int i = 1 ; i < n; i++)
    {

        //cout << pom[i] << " ";
        if((prev - pom[i])*parity <= 0)
        {
            pom[i] = -parity * INF;
            change++;
        }
        parity *= -1;
        prev = pom[i];
        //cout << pom[i] << "\n";
    }
    //cout << "\n";

    return change;

}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int n; cin >> n;
    for(int i = 0 ; i < n; i++)
    {
        cin >> kopia1[i];
        kopia2[i] = kopia1[i];
    }

    ll ans = INF;

    ans = min(check(n,kopia1,-1), check(n,kopia2,1));

    cout << ans;



}