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#include <bits/stdc++.h>

using namespace std;

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(int i = 0; i < n; i++){
        cin >> a[i];
    }
    int last = a[0];
    int ans = 0;
    for(int i = 1; i < n; i++){
        if(i % 2){
            if(a[i] >= last){
                ans++;
                last = -10000000;
            }else{
                last = a[i];
            }
        }else{
            if(a[i] <= last){
                ans++;
                last = 10000000;
            }else{
                last = a[i];
            }
        }
    }
    int best = ans;
    ans = 0;
    last = a[0];
    for(int i = 1; i < n; i++){
        if(i % 2 == 0){
            if(a[i] >= last){
                ans++;
                last = -10000000;
            }else{
                last = a[i];
            }
        }else{
            if(a[i] <= last){
                ans++;
                last = 10000000;
            }else{
                last = a[i];
            }
        }
    }
    cout << min(ans, best) << endl;
    return 0;
}