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#include <bits/stdc++.h>     
using namespace std;
 
#define st first
#define nd second
#define g0 get<0> 
#define g1 get<1> 
#define g2 get<2> 
#define double long double


main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	int n;
	cin>>n;
	vector<int> v(n), v2;
	for(int i=0; i<n; i++)
		cin>>v[i];
	v2=v;
	int r1=0;
	bool du=0;
	for(int i=0; i<n-1; i++)
	{
		if(du==0 && v2[i+1]<=v2[i]){
			r1++;
			v2[i+1]=INT_MAX;
		}
		if(du==1 && v2[i+1]>=v2[i]){
			r1++;
			v2[i+1]=INT_MIN;
		}
		du=!du;
	}
	int r2=0;
	du=1;
	v2=v;
	for(int i=0; i<n-1; i++)
	{
		if(du==0 && v2[i+1]<=v2[i]){
			r2++;
			v2[i+1]=INT_MAX;
		}
		else if(du==1 && v2[i+1]>=v2[i]){
			r2++;
			v2[i+1]=INT_MIN;
		}
		
		du=!du;
	}
	cout<<min(r1, r2);
	
}