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#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
const int maxn = 1e9;
const int MAX_N = 1e6 + 7;
vector<int> a(MAX_N);
vector<int> b(MAX_N);

int main(){
//ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int n; cin >> n;
	rep(i,n){
		cin >> a[i];
		b[i] = a[i];
	}
	//pierwszy rosnie
	int cnt1 = 0;
	for(int i = 1; i < n; i++){
		if(i%2 == 1){
			if(a[i] <= a[i-1]){
				cnt1++;
				a[i] = maxn;
			}
		}
		else{
			if(a[i] >= a[i-1]){
				cnt1++;
				a[i] = -maxn;
			}
		}
	}
	//pierwszy maleje
	int cnt2 = 0;
	for(int i = 1; i < n; i++){
		if(i%2 == 0){
			if(b[i] <= b[i-1]){
				cnt2++;
				b[i] = maxn;
			}
		}
		else{
			if(b[i] >= b[i-1]){
				cnt2++;
				b[i] = -maxn;
			}
		}
	}
	cout << min(cnt1,cnt2);
	return 0;
}