#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>
#include<queue>
#include<cmath>
#include<algorithm>
using namespace std;
int n,a[10000][10000],ans=0;
int main(){
	cin >>n;
	a[0][1]=1;
	a[1][0]=1;
	a[1][1]=1;
	for(int i=1;i<n;i++){
		for(int j=1;j<i;j++){
			if(i!=j&&(i%2!=0||j%2!=0)){
				a[i][j]=1;
				ans++;
			}
		}
	}
	cout <<ans*2+3;
	return 0;
}