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//dzien1 - B
#include <bits/stdc++.h>
using namespace std;

int tab1[50005];
int tab2[50005];

int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	
	int n;
	cin >> n;
	
	int result1 = 0, result2 = 0;
	
	for(int i=0; i<n; i++)
	{
		int a;
		cin >> a;
		tab1[i] = a;
		tab2[i] = a;
	}
	
	for(int i=1; i<n; i++)
	{
		if(i%2 == 0)
		{
			if(tab2[i] <= tab2[i-1]) {result2++; tab2[i] = 1000002;}
			if(tab1[i] >= tab1[i-1]) {result1++; tab1[i] = -1000002;}
		}
		if(i%2 == 1)
		{
			if(tab1[i] <= tab1[i-1]) {result1++; tab1[i] = 1000002;}
			if(tab2[i] >= tab2[i-1]) {result2++; tab2[i] = -1000002;}
		}
	}
	
	cout<<min(result1, result2);
	
	return 0;
}