#include<stdio.h>
#include<math.h>
long v[1000001],k;
int tot(long n)
	{
	long i;
	long s=1;
	s=n;
	i=3;
	if (n%2==0) s=s-s/2;
	else if (v[n]==0) s=s-s/n;
	else
	while(i<=n)
		{
		if (v[i]==0&&n%i==0) s=s-s/i;
		if (i>n) break;
		i=i+2;}
	return s;}

int main()
{long nr,n,i,sol=0,j;
FILE*f=fopen("fractii.in","r");
FILE*g=fopen("fractii.out","w");
fscanf(f,"%ld",&n);
for (i=2;i<=500000;i++) v[2*i]=1;
i=3;
while (i<=sqrt(n))
	{if (v[i]==0)
		{j=i*i;
		while(j<=n) {v[j]=1; j=j+2*i;}}
	i+=2;}
sol=1;
for (i=2;i<=n;i++) sol+=2*tot(i);
fprintf(g,"%ld",sol);
fclose(f);
fclose(g);
return 0;}