#include <iostream>
using namespace std;
int main()
{ int n,br,i,j;
cin>>n;
br=0;
for ( i = 2; i < n;++i)
{
if ( i%2==0 and i+(n-i)==n)
br++;}
cout<<br<<endl;
return 0;
}
#include <iostream>
using namespace std;
int main()
{ int n,br,i,j;
cin>>n;
br=0;
for ( i = 2; i < n;++i)
{
if ( i%2==0 and i+(n-i)==n)
br++;}
cout<<br<<endl;
return 0;
}