#include<stdio.h>
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	int k,i,j,n1,n2,n,nr=1;
	scanf("%d",&n);
	for(i=2;i<=n;i++)
	{
	 n1=1;
	 n2=1;
	 k=i;
	 if(!(k%2)) 
		{
		 while(!(k%2))
			k/=2;
		 n2*=2;
		}
		for(j=3;j<=i;j+=2)
	    if(!(k%j))
			{
			 while(!(k%j))
				k/=j;
			 n1*=(j-1);
			 n2*=j;
			}
		nr=nr+(i*n1/n2)*2;
	}
	printf("%d",nr);
	return 0;
}