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#include <bits/stdc++.h>
using namespace std;

int main(){
	cin.tie(0);
	int n;
	cin>>n;
	vector<int>a(n);
	for(int i=0;i<n;i++)
		cin>>a[i];
	vector<int>b(n);
	b=a;
	int inf=1e6+1;
	int res1=0;
	//GDGD...
	for(int i=1;i<n;i++){
		if(i%2==1 and b[i]<=b[i-1]){
			res1++;
			b[i]=inf;
		}
		else if(i%2==0 and b[i]>=b[i-1]){
			res1++;
			b[i]=-inf;
		}
	}
	int res2=0;
	b=a;
	//DGDG...
	for(int i=1;i<n;i++){
		if(i%2==1 and b[i]>=b[i-1]){
			res2++;
			b[i]=-inf;
		}
		else if(i%2==0 and b[i]<=b[i-1]){
			res2++;
			b[i]=inf;
		}
	}
	cout<<min(res1,res2)<<'\n';
}