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#include <iostream>
#include <climits>
using namespace std;

const int MAXN = 5e4+1;
const int INF = 1e9;
int a[MAXN], b[MAXN];

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	
	int n;
	cin >> n;
	for (int i=1; i<=n; i++){ cin >> a[i]; b[i] = a[i];}
	// 1 przypadek : a[1] > a[2]
	int ans1 = 0;
	bool r = true;
	if (a[1] <= a[2]){ ans1++; a[2] = -INF;}
	for (int i=3; i<=n; i++){
		if (r){
			if (a[i] <= a[i-1]){ ans1++; a[i] = INF;}
			r = false;
		} else{
			if (a[i] >= a[i-1]){ ans1++; a[i] = -INF;}
			r = true;
		}
	}
	
	// 2 przypadek: b[2] > b[1]
	int ans2 = 0;
	r = false;
	if (b[2] <= b[1]){ ans2++; b[2] = INF;}
	for (int i=3; i<=n; i++){
		if (r){
			if (b[i] <= b[i-1]){ ans2++; b[i] = INF;}
			r = false;
		} else{
			if (b[i] >= b[i-1]){ ans2++; b[i] = -INF;}
			r = true;
		}
	}
	
	cout << min(ans1, ans2) << "\n";
}