#include <stdio.h>
#define NMAX 6000000

unsigned long long  t[NMAX];
unsigned long n, i;

int main()
{
    freopen("12perm.in","r",stdin);
    freopen("12perm.out","w",stdout);

    scanf("%lu", &n);
   
    t[1]=1;
    t[2]=2;
    t[3]=6;
    t[4]=12;
	
	for (i=5; i<=n; ++i)
	    t[i]=t[i-1]+t[i-3]+2*(i-2);
	 
    printf("%llu\n", t[n]);
    

    fclose(stdin);
    fclose(stdout);

    return 0;
}