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#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
std::vector<int> v;
int n;
int changes(bool up, bool dummy)
{
  int res = 0;
  if (dummy)
    res++;
  for (int i=1;i<n;i++)
  {
    up = !up;
    if (dummy==true)
    {
      dummy = false;
      continue;
    }
    if (up && v[i-1] < v[i])
      continue;
    if (!up && v[i-1] > v[i])
      continue;
    dummy = true;
    res++;
  }
  return res;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n;
    v.resize(n);
    for (int i=0;i<n;i++)
      cin >> v[i];
    
    int res = std::min(n, changes(true, false));
    res = std::min(res, changes(false,false));
    if (v.size()%2)
    {
      res = std::min(res, changes(false,true));
      res = std::min(res, changes(true,true));
    }
    std::cout << res << std::endl;
}