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#include <bits/stdc++.h>
using namespace std;
constexpr int MAX_N = 50003; 
int n,a[MAX_N],changed[MAX_N],value_odd,value_even;

int main()
{
	scanf("%d",&n);
	for(int i = 1;i<=n;++i)
	{
			scanf("%d",&a[i]);
	}
	for(int i =1;i<=n;++i)changed[i] = a[i];
	if(a[1] == 1e9)
	{
		++value_odd;
		changed[1] =-1e9;
	}
	for(int i = 2;i<=n;++i)
	{
		if(i%2)
		{
			if(changed[i - 1] <= a[i])
			{
				value_odd++;
				changed[i] = -1e9;
			}
		}
		else
		{
			if(changed[i - 1] >= a[i])
			{
				value_odd++;
				changed[i] = 1e9;
			}
		}
	}
	for(int i =1;i<=n;++i)changed[i] = a[i];
		if(a[1] == -1e9)
	{
		++value_even;
		changed[1] = 1e9;
	}
	for(int i = 2;i<=n;++i)
	{
		if(i%2)
		{
			if(changed[i - 1] >= a[i])
			{
				value_even++;
				changed[i] = 1e9;
			}
		}
		else
		{
			if(changed[i - 1] <= a[i])
			{
				value_even++;
				changed[i] = -1e9;
			}
		}
	}
	printf("%d",min(value_even,value_odd));
}