#include<stdio.h>
long n;
long long nr;
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");

void rez()
{
  long i,j;
 nr=0; 
  nr+=2*n-1;
 int sw=0;int sw2=0;
 if(n%2==0)
 sw=1;
 else sw2=1;

 for(i=2;i<=n;i++)
  if(i%2==0)
  nr+=(n-sw)/2;
   else nr+=(n-sw2)/2;
}

  


int main()
{ 
  fscanf(f,"%ld",&n);
   rez();
  fprintf(g,"%ld",nr);
 return 0;
}