#include <cstdio>

int v[1000000];

int main()
{
	int n,i,j;
	long long sum=0;
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
    for (i=2;i<=n;++i)
			for (sum+=i+v[i]-1,j=i+i;j<=n;j+=i) v[j]-=i-1+v[i];
		
			
	printf("%lld",1+2*sum);
return 0;}