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#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int count_changes(int &n, vector<int> a, int direction) {
  int changes = 0;

  for (int i=1; i<n; i++) {
    if ((a[i] - a[i - 1]) * direction <= 0) {
      a[i] = 10000000 * direction;
      changes++;
    }

    direction *= -1;
  }

  return changes;
}

int main() {
  int n;
  vector<int> a;

  scanf("%d", &n);
  a.resize(n);

  for (int i=0; i<n; i++) {
    scanf("%d", &a[i]);
  }

  printf("%d\n", min(count_changes(n, a, 1), count_changes(n, a, -1)));

  return 0;
};