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

int n;
int t[50000];
int t1[50000];
void read() {
    cin>>n;
    for(int i = 0;i<n;i++){
        cin>>t[i];
    }
}


void solve() {
    read();
    const int MAXX = 1000000000;
    const int MINN = -1000000000;

    t1[0]=t[0];
    int wynik = 0;
    for(int i = 1; i < n; i++) {
        t1[i] = t[i];
        if(i%2) {
            if(t[i]<=t1[i-1]) {
                wynik++;
                t1[i] = MAXX;
            }
        } else {
            if(t[i]>=t1[i-1]) {
                wynik++;
                t1[i] = MINN;
            }
        }
    }
    int wynik2 = 0;
    for(int i = 1; i < n; i++) {
        t1[i] = t[i];
        if(i%2==0) {
            if(t[i]<=t1[i-1]) {
                wynik2++;
                t1[i] = MAXX;
            }
        } else {
            if(t[i]>=t1[i-1]) {
                wynik2++;
                t1[i] = MINN;
            }
        }
    }
    cout<<min(wynik,wynik2)<<"\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    solve();
    return 0;
}