#include <iostream>
  #include <stdio.h>
  using namespace std;


  int signOf(int value) {
    return value > 0 ? 1 : value < 0 ? -1 : 0;
  }

  int main() {
    int n;
    cin >> n;

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

    int signs[n];
    for (int i = 0; i < n - 1; i++) {
      signs[i] = signOf(tones[i + 1] - tones[i]);
    }

    int downErrors = 0;
    for (int i = 0; i < n - 1; i++) {
      int expectSign = (i % 2) * 2 - 1;
      if (signs[i] != expectSign) {
        downErrors++;
        i++;
      }
    }

    int upErrors = 0;
    for (int i = 0; i < n - 1; i++) {
      int expectSign = -((i % 2) * 2 - 1);
      if (signs[i] != expectSign) {
        upErrors++;
        i++;
      }
    }

    printf("%d", upErrors < downErrors ? upErrors : downErrors);
    return 0;
  }