O_o Water
#include <iostream>
using namespace std;
int main()
{
int n;
scanf("%d",&n);
int a[n];
for(int i=0;i<n;i++)
scanf("%d",&a[i]);
int ans =0 ;
for(int i=0;i + 2 < n;i++)
{
if(a[i] > a[i+1] && a[i+2] > a[i+1] || a[i] < a[i+1] && a[i+1] > a[i+2])
ans++;
}
cout<<ans;
return 0;
}