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#include <bits/stdc++.h>


using namespace std;


int main(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	int n;
	cin >> n;
	vector<int> a(n);
	for (int i = 0; i < n; i++) cin >> a[i];
	int opa = 0, opb = 0;
	bool changed = false;
	for (int i = 1; i < n; i++){
		if (((i%2 && a[i] >= a[i-1]) || (!(i%2) && a[i] <= a[i-1])) && !changed){
			opa++;
			changed = true;
		}
		else{
			changed = false;
		}
	}
	changed = false;
	for (int i = 1; i < n; i++){
		if (((!(i%2) && a[i] >= a[i-1]) || (i%2 && a[i] <= a[i-1])) && !changed){
			opb++;
			changed = true;
		}
		else{
			changed = false;
		}
	}
	cout << min(opa,opb);
	return 0;
}