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#include <iostream>
#include <vector>
#include <climits>

using namespace std;

int part_result(int const ver, vector<int> const & vec, int const n) {
    int result = 0;
    int last = vec[0];
    for(int i = 1; i < n; i++) {
        if(i%2 == ver) {
            if(last >= vec[i]) {
                result++;
                last = INT_MAX;
            } else {
                last = vec[i];
            }
        } else if (i%2 == 1-ver) {
            if(last <= vec[i]) {
                result++;
                last = INT_MIN;
            } else {
                last = vec[i];
            }
        }
    }

    return result;
}

void solve() {
    int n;
    cin >> n;

    vector<int> vec(n);
    for(int i = 0; i < n; i++) {
        cin >> vec[i];
    }

    int result0 = part_result(0, vec, n);
    int result1 = part_result(1, vec, n);
    
    cout << ((result0 < result1) ? result0 : result1) << "\n";
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    solve();

    return 0;
}