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#include <iostream>
#include <vector>

using namespace std;

struct Comparison {
    bool reversed;
    
    Comparison(bool _reversed) : reversed(_reversed) {}
    
    bool satisfied(int a, int b) {
        if (reversed) {
            return a > b;
        }
        else {
            return a < b;
        }
    }
    
    int to_satisfy() {
        if (reversed) return -1000000000;
        else return 1000000000;
    }
    
    void reverse() {
        reversed = !reversed;
    }
};

int count_corrections(const vector<int>& a, Comparison comp) {
    size_t i = 1;
    int prev = a[0];
    int corrections = 0;
    
    while (i < a.size()) {
        if (comp.satisfied(prev, a[i])) {
            prev = a[i];
        } else {
            prev = comp.to_satisfy();
            corrections++;
        }
        comp.reverse();
        i++;
    }
    return corrections;
}

int main() {
    ios_base::sync_with_stdio(0);
    
    int n; cin >> n;
    vector<int> a(n);
    
    for (int i =0; i < n; ++i)
        cin >> a[i];
        
    int x = count_corrections(a, Comparison(false));
    int y = count_corrections(a, Comparison(true));
    
    if (x > y) cout << y << endl;
    else cout << x << endl;
    
    return 0;
}