#include <bits/stdc++.h>
int main(void) {
  int n;
  int a[1100];
  while (scanf("%d", &n) == 1) {
    for (int i = 0; i < n; i++) scanf("%d", a + i);
    int cnt = 1, ans = 0;
    int j = 0;
    if (n <= 2) {
      printf("%d\n", ans);
      break;
    }
    if (a[0] > a[1])
      j = -1;
    else if (a[0] == a[1])
      j = 0;
    else
      j = 1;
    while (cnt < n - 1) {
      if (j == -1) {
        for (; cnt < n - 1 && a[cnt] > a[cnt + 1]; cnt++)
          ;
        if (cnt == n - 1) break;
        if (a[cnt] > a[cnt + 1])
          j = -1;
        else if (a[cnt] == a[cnt + 1])
          j = 0;
        else {
          ans++;
          j = 1;
        }
      }
      if (j == 0) {
        for (; cnt < n - 1 && a[cnt] == a[cnt + 1]; cnt++)
          ;
        if (cnt == n - 1) break;
        if (a[cnt] > a[cnt + 1])
          j = -1;
        else if (a[cnt] == a[cnt + 1])
          j = 0;
        else
          j = 1;
      }
      if (j == 1) {
        for (; cnt < n - 1 && a[cnt] < a[cnt + 1]; cnt++)
          ;
        if (cnt == n - 1) break;
        if (a[cnt] > a[cnt + 1]) {
          ans++;
          j = -1;
        } else if (a[cnt] == a[cnt + 1])
          j = 0;
        else
          j = 1;
      }
    }
    printf("%d\n", ans);
  }
  return 0;
}
