#include<stdio.h>
long n,c,i,d=0;

int main()
{
  FILE *f=fopen("fractii.in", "r");
  FILE *g=fopen("fractii.out", "w");
  while(!feof(f))
  {
    fscanf(f, "%d", &n);
    if(n==1) { fprintf(g, "%d", 1); return 0;}
    if(n==2) { fprintf(g, "%d", 3); return 0;}
    c=3;
    for(i=2; i<=n-1; i++)
      {
	if(i%2==0) d=c+4*(i/2);
	else
	d=c+4;
        c=d;
      }
    fprintf(g, "%d", d);
  }
  fclose(g);
  return 0;
}