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#define _CRT_SECURE_NO_WARNINGS

#include <cstdio>
#include <stdio.h>
#include <iostream>
#include <string.h>
#include <math.h>
#include <algorithm>
#include <vector>
#include <map>

constexpr int MAX_N = 50000;
constexpr auto MAX_VAL = 10e9 + 1;
constexpr auto MIN_VAL = -10e9 - 1;

inline int GetNumberOfSwaps(std::vector<double> allTones, bool nextShouldBeLower)
{
    double prevTone = allTones[0];    
    int cnt = 0;    
    for (auto i = 1; i < allTones.size(); i++)
    {
        auto curTone = allTones[i];
        if (nextShouldBeLower && curTone >= prevTone)
        {
            curTone = MIN_VAL;
            cnt++;
        }
        else if (!nextShouldBeLower && curTone <= prevTone)
        {
            curTone = MAX_VAL;
            cnt++;
        }
        nextShouldBeLower = !nextShouldBeLower;
        prevTone = curTone;
    }
    return cnt;
}

int main()
{
	int n;
	auto _ = scanf("%d\n", &n);
    std::vector<double> allTones;
	for (auto i = 0; i < n; i++)
	{
		int tone;
		auto _ = scanf("%d_", &tone);
        allTones.push_back(tone);
	}
    int result = std::min(GetNumberOfSwaps(allTones, true), GetNumberOfSwaps(allTones, false));    
    
	printf("%d\n", result);
	return 0;
}