#include<fstream.h>

ifstream f ("fractii.in");
ofstream g ("fractii.out");

long n, p, q;

int cmmdc(int a, int b)
 {  int r=a%b;
    while(r)
     {    a = b;
	  b = r;
	  r = a%b;
     }
    return b;
 }

void calcul()
 {   int nr=0;
     for(p=1; p<=n; p++)
      {  if(p==1) nr = nr+n;
	 if(p%2 && p!=1) nr = nr+n-1;
	 if(p%2==0 && n%2) nr = nr+n-2;
	 if(p%2==0 && n%2==0) nr = nr+n-2;
      }
     g << nr << "\n";
 }

int main()
 {  f >> n;
    calcul();
    return 0;
 }