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#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <chrono>
#include <functional>
using namespace std;

int computeBad(std::vector<int> numbers, std::function<bool(int, int, int)> isBad)
{
  int badNumberSize = 0;
  int result = 0;
  for (unsigned long long i = 0; i < numbers.size() - 1; ++i)
  {
    if (isBad(numbers[i], numbers[i + 1], (int)i))
    {
      ++badNumberSize;
    }
    else
    {
      result += (badNumberSize+1) / 2;
      badNumberSize = 0;
    }
  }
  result += (badNumberSize + 1) / 2;
  return result;
}

int main()
{
  ios::sync_with_stdio(false);
  int n;
  std::cin >> n;
  std::vector<int> numbers;
  for (int i = 0; i < n; ++i)
  {
      int number;
      std::cin >> number;
      numbers.push_back(number);
  }
  int firstResult = computeBad(numbers, [](int elem, int next, int position) 
  {
    if (position % 2 == 0)
      return elem <= next;
    else
      return elem >= next;
  });
  int secondResult = computeBad(numbers, [](int elem, int next, int position)
    {
      if (position % 2 == 0)
        return elem >= next;
      else
        return elem <= next;
    });
  std::cout << std::min(firstResult, secondResult);
  return 0;
};