#include <iostream>
using namespace std;
int main() {
// your code goes here
int n1=10000,n2=10000,n3,n,g=0;
scanf("%d",&n);
while(n--)
{
scanf("%d",&n3);
if(n1<n2 && n2>n3)g++;
n1=n2;
n2=n3;
}
printf("%d",g);
return 0;
}
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