inline bool kadomatu(int a,int b,int c){
  return a!=b&&b!=c&&c!=a&&((a<b && c<b)||(a>b && c>b));
}

{
  int i,n,a[100],c=0;
  rd(n,a(n));
  c += kadomatu(a[0..n-3], a[1..], a[2..]);
  wt(c);
}