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#include <bits/stdc++.h>
using namespace std;
using LL = long long;
#define FOR(i, l, r) for (auto i = (l); i <= (r); ++i)
#define REP(i, n) FOR (i, 0, (n)-1)
#define ssize(x) int(x.size())
template<class A, class B>
auto&
operator<<(ostream& o, pair<A, B> p)
{
  return o << "(" << p.first << ", " << p.second << ")";
}
template<class T>
auto
operator<<(ostream& o, T x) -> decltype(x.end(), o)
{
  o << "{";
  int i = 0;
  for (auto e : x) o << (", ") + 2 * !i++ << e;
  return o << "}";
}
#ifdef DEBUG
#define debug(x...)                                                            \
  cerr << "[" #x "]: ", [](auto... $) { ((cerr << $ << "; "), ...); }(x),      \
    cerr << '\n'
#else
#define debug(...)                                                             \
  {                                                                            \
  }
#endif

#define MAX 1000000000
#define MIN -1000000000

int
assume(bool if_up, vector<int> seq)
{
  int moves = 0;

  // Set first two values
  if (if_up && seq[0] >= seq[1])
    moves++, seq[1] = MAX;
  else if (!if_up && seq[0] <= seq[1])
    moves++, seq[1] = MIN;

  // Force alternation
  for (int i = 2; i < seq.size(); ++i, if_up = !if_up)
    if (if_up && seq[i - 2] < seq[i - 1] && seq[i - 1] <= seq[i])
    {
      moves++;
      seq[i] = MIN;
      debug(i, MIN);
    }
    else if (!if_up && seq[i - 2] > seq[i - 1] && seq[i - 1] >= seq[i])
    {
      moves++;
      seq[i] = MAX;
      debug(i, MAX);
    }
  debug(if_up, moves);
  return moves;
}

int
main()
{
  cin.tie(0)->sync_with_stdio(0);

  int n;
  vector<int> seq;
  cin >> n;
  seq.resize(n);
  for (auto& x : seq) cin >> x;

  cout << min(assume(false, seq), assume(true, seq)) << "\n";
  return 0;
}