#include<stdio.h>
int x;
int a[1000001];
int main()
{
	long long s=0;
	int n;
	FILE *in,*out;
	in=fopen("fractii.in","r");
	out=fopen("fractii.out","w");
	
	fscanf(in,"%d",&n);

	for(int i=0;i<1000001;i++)a[i]=i;
	for(int i=0;i<1000001;i++)
		if(a[i]==i)
		for(int j=2;j*i<1000001;j++)a[j*i]=a[j*i]/i;

	
	s=1;
	for(int i=1;i<=n;i++)
		s+=2*a[i];

	fprintf(out,"%lld",s);
	fclose(in);
	fclose(out);
	return 0;
}