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#include <iostream>

using namespace std;

int main() {

  int n;
  cin >> n;

  int a[50007];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }

  int result1 = 0;
  bool prev = false;
  for (int i = 1; i < n; i++) {
    if (i % 2 == 0) {
        if (a[i - 1] >= a[i] && !prev) {
          result1++;
          prev = true;
        } else {
          prev = false;
        }
    } else {
      if (a[i - 1] <= a[i] && !prev) {
        result1++;
        prev = true;
      } else {
        prev = false;
      }
    }
  }

  int result2 = 0;
  prev = false;
  for (int i = 1; i < n; i++) {
    if (i % 2 == 1) {
      if (a[i-1] >= a[i] && !prev) {
        result2++;
        prev = true;
      } else {
        prev = false;
      }
    } else {
      if (a[i-1] <= a[i] && !prev) {
        result2++;
        prev = true;
      } else {
        prev = false;
      }
    }
  }

  cout << min(result1, result2) << endl;

  return 0;
}