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#if defined(EMBE_DEBUG) && !defined(NDEBUG)
#include "embe-debug.hpp"
#else
#define LOG_INDENT(...) do {} while (false)
#define LOG(...) do {} while (false)
#define DUMP(...) do {} while (false)
#endif

#include <iostream>
using namespace std;

namespace {

constexpr int inf = 1'000'000'000;

struct State {
  int value;
  bool increasing;
  int res;

  void process(int x)
  {
    if ((increasing && x > value) || (!increasing && x < value)) {
      value = x;
    } else {
      value = increasing ? inf : -inf;
      res += 1;
    }
    increasing = !increasing;
  }

  explicit State(bool increasing_): value{increasing_ ? -inf : inf}, increasing{increasing_}, res{0} {
  }
};

}

int main()
{
  iostream::sync_with_stdio(false);
  cin.tie(nullptr);

  State states[] = {State(false), State(true)};

  int n;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    int x;
    cin >> x;


    for (auto& state: states) {
      state.process(x);
    }
  }

  int res = min(states[0].res, states[1].res);
  cout << res << endl;

  return 0;
}