#include <stdio.h>
#include <stdlib.h>

#define max 1000000/2/8 + 1

int main()
{
	FILE *f = fopen("fractii.in","rt"), 
	     *g = fopen("fractii.out","wr");

	int n;
	fscanf(f,"%i",&n);
	char c[max];
	int cate= n,i;

	if (n == 1) 
		fprintf(g,"%i",cate);
	else 
	{
		cate+=n-1 ;
		for (i = 2; i <= n; i++){
			cate+=(((n/i -1)*(i-1)  + n%i)*2);
		}
		fprintf(g,"%i",cate);
	}	
 	

	fclose(f);
	fclose(g);


	return 0;
}