tijei

#include <iostream>
using namespace std;
int main(){
int ans=0;
int n;
cin >> n;
for(int a=1;a<=n;a++){
for(int b=a+1;b<=n;b++){
for(int c=b+1;c<=n;c++){
if(a+b+c==n){
ans++;
}
}
}
}
cout<<ans<<endl;
return 0;
}