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

const int MAX_N = 5e5+7;

int n, c, b, tab[MAX_N];

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin>>n;
    for (int i = 0; i < n; i++) {
        cin>>tab[i];
    }

    for (int i = 1; i < n; i++) {
        if (i%2==1) {
            if (tab[i-1]<=tab[i]) {
                b++;
                i++;
            }
        }
        else {
            if (tab[i-1]>=tab[i]) {
                b++;
                i++;
            }
        }
    }

    for (int i = 1; i < n; i++) {
        if (i%2==0) {
            if (tab[i-1]<=tab[i]) {
                c++;
                i++;
            }
        }
        else {
            if (tab[i-1]>=tab[i]) {
                c++;
                i++;
            }
        }
    }

    //cout<<b<<" "<<c;
    cout<<min(b, c);
}