#include <iostream>

using namespace std;

int main()
{
int n,br,i,j;
cin>>n;
br=0;
for ( i = 2; i <= n;++i)
{
for (j = 1; j <= n;++j)
if (i+j==n && i%2==0)
br++;}
cout<<br<<endl;
return 0;
}

2.nacin

#include <iostream>

using namespace std;

int main()
{
int i,n,br,r;
cin>>n;
br=0;
for(i=1;i<n/2;i++)
{
if(2*i+(n-(2*i))==n)
br=br+1;
}
if(n%2==0)
cout<<br;
else
cout<<br+1;
return 0;
}