#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N=200010;

ll n;

ll s;

ll a[N];

int main()
{
	scanf("%lld",&n);
	
	for(int i=1;i<=n;++i)
	{
		scanf("%lld",&a[i]);
	}
	
	for(int i=1;i<=n;i++)
	{
		if(a[i-1]>a[i]&&a[i+1]>a[i]) 
		{
			++s;
		}
	}
	printf("%lld",s);
	return 0;
}