#include<bits/stdc++.h>
 
using namespace std;
int arr[10003];
 
int main()
{
    int n,i,counter,tag;
    while(scanf("%d",&n)&&n)
    {
        counter=0;
 
        for(i=1; i<=n; i++)
        {
            scanf("%d",&arr[i]);
        }
 
        if(arr[2]>arr[1])
        {
            tag=1;
        }
        else if(arr[2]<arr[1])
        {
            tag=0;
        }
 
        for(i=1; i<n; i++)
        {
            if(arr[i+1]>arr[i] && tag==1)
            {
                counter++;
                tag=0;
 
            }
            else if(arr[i+1]>arr[i] && tag==0)
            {
                continue;
            }
            else if(arr[i+1]<arr[i] && tag==0)
            {
                counter++;
                tag=1;
            }
            else if(arr[i+1]<arr[i] && tag==1)
            {
                continue;
            }
        }
 
        if(arr[n-1]<arr[n] && arr[2]>arr[1])
        {
            counter++;
 
        }
        else if(arr[n-1]>arr[n] && arr[2]<arr[1])
        {
            counter++;
        }
        printf("%d\n",counter);
    }
    return 0;
}