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#include <iostream>
using namespace std; 
int tab[50002];
int tab2[50002];
int main() 
{
  int n; cin >> n;  
  for (int i = 0; i < n; i++)
  {
    cin >> tab[i];
    tab2[i] = tab[i];
  }
  int w1 = 0; 
  for (int i = 0; i < n; i++)
  {
    if (i%2==0)
    {
      if (tab[i] <= tab[i+1])
      {
        w1++; 
        tab[i+1] = -1000001;
      }
    }
    if (i%2==1)
    {
      if (tab[i] >= tab[i+1])
      {
        w1++;
        tab[i+1] = 1000001;
      }
    }
  }
  int w2 = 0; 
  for (int i = 0; i < n; i++)
  {
    if (i%2==1)
    {
      if (tab2[i] <= tab2[i+1])
      {
        w2++;
        tab2[i+1] = 1000001;
      }
    }
    if (i%2==0)
    {
      if (tab2[i] >= tab2[i+1])
      {
        w2++;
        tab2[i+1] = -1000001;
      }
    }
  }
  if (w2>w1)
  {
    cout << w1;
  }
  else
  {
    cout << w2;
  }
}