#include <stdio.h>
#include <string.h>
#define N 1000001
char prim[1000001];
void ciurul(int max)
{
	int nn=max>>1,i,j;
	prim[0]=1;
	prim[1]=1;
	for (i=2; i<=nn; i++)
		for (j=i+i; j<=max; j+=i)
			prim[j]=1;
}

int euler(int n)
{
	int i;
	int	p=n;
	
	for (i=2; i<=n; i++)
		if (!prim[i]&&!(n%i))
			p=p*(i-1)/i;
	return p;
}

int main()
{
	int n,i;
	long rez=1;
	
	FILE *in=fopen("fractii.in","r");
	fscanf(in,"%d",&n);
	fclose(in);
	
	ciurul(n);
	for (i=2; i<=n; i++)
		rez+=2*euler(i);
		
	FILE *out=fopen("fractii.out","w");
	fprintf(out,"%ld\n",rez);
	fclose(out);
	
	return 0;
}