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#include <iostream>
using namespace std;

int main() {
    int changes = 0, changes2 = 0, n, a;
    cin >> n;
    int tab[n];
    int tab2[n];
    for (int i = 0; i < n; i++){
        cin >> a;
        tab[i] = a;
        tab2[i] = a;
    }

    bool nextSmaller = false;

    if (tab[0] < tab[1])
        nextSmaller = true;
    else if (tab[0] == tab[1]) {
        tab[1] = -1000000000;
        changes++;
    }

    for (int i = 1; i < n - 1; i++) {
        
        if (nextSmaller && tab[i] <= tab[i + 1]) {
            tab[i + 1] = -1000000000;
            changes++;
        }
        else if (!nextSmaller && tab[i] >= tab[i + 1]) {
            tab[i + 1] = 1000000000;
            changes++;
        }
        nextSmaller = !nextSmaller;
    }
    
    nextSmaller = false;

    if (tab2[n-2] > tab2[n-1])
        nextSmaller = true;
    else if (tab2[n-2] == tab2[n-1]) {
        tab2[n-1] = -1000000000;
        changes2++;
    }
    
    for (int i = n-1; i >= 1; i--) {
        
        if (nextSmaller && tab2[i - 1] <= tab2[i]) {
            tab2[i - 1] = 1000000000;
            changes2++;
        }
        else if (!nextSmaller && tab2[i - 1] >= tab2[i]) {
            tab2[i + 1] = -1000000000;
            changes2++;
        }
        nextSmaller = !nextSmaller;
    }
    
	cout<<min(changes,changes2);
	
    return 0;
}