#include<stdio.h>

int A[1000001];
int T[1000001];
int N;
long long sum = 1;

int main()
{
	FILE *f = fopen("fractii.in","r");
	FILE *g = fopen("fractii.out","w");
	
	fscanf(f,"%d ",&N);
	for(int i=2;i<=N;i++)
	{
		long int a;
		sum += (i-1-A[i])*2;
		if(!A[i])
			for(int j=i+i,a = 1;j<=N;j+=i,a ++)
			{
				A[j] += a;
				T[j] ++;
			}
	}
	for(int i=1;i<=N;i++)
		printf("%d -> %d\n",i,A[i]);
	fprintf(g,"%llu",sum);
	
	fclose(g);
	fclose(f);
}